v5.1.2

I didn't really mean to push this build, but it seems 5.1.1 was built wrong for some reason, and (still can't see why), it causes issues with local play in games such as Smash Bros and New Super Mario Bros 2.
The same code worked fine from a different build.
So here's a quick rebuild. The only changes from 5.1.1 were a general code cleanup and a FatFs update, nothing too fancy.

v5.1.1

• Fixed the L+SELECT payload not working, this was due to the LFN -> SFN (8.3) conversion. Now the payload must be named sel_NAME.bin.
• Removed LFN support from the FatFs of the chainloader (as LFNs aren't used at all by it). This shrinks down the binary by ~4 KBs.

Note, you don't need to update if you didn't use the L+SELECT payload or if you aren't obsessed by the binary's size :)

v5.1

• Changed the payload chainloader to load payloads named "BUTTON_NAME.bin". As an example: "up_Decrypt9.bin". "default.bin" was changed to "def_NAME.bin" ("NAME" can also be omitted). Original idea and code are by @habbbe, so thanks!
• Fixed bug when exiting AGB_FIRM and not having an updated SysNAND, where the last used FIRM would be remembered incorrectly, thus loading 9.0 FIRM and forcing the user to reboot to play a GBA game again.

v5.0

• The way AuReiNand works has changed. Now you can specify to autoboot SysNAND or not, and a NAND is no more tied to a FIRM (since 9.0 FIRM is autodetected). If you press nothing the default NAND is booted with its own FIRM, L boots the non-default NAND with its own FIRM, R boots EmuNAND with the SysNAND FIRM if you picked "Use SysNAND FIRM as default", and vice-versa.
• Gotten rid of the patched FIRMs, AuReiNand now finds and loads all the FIRMs from CTRNAND by default. If you are booting an emuNAND, the FIRM will also be loaded from its CTRNAND by default. This applies to AGB and TWL FIRM too, and allows for a very fast boot with no firmware files on the SD card.
• If for some reason (like using NTR) you do not want to use the CTRNAND FIRM, you can place a firmware.bin in the aurei folder and it will be loaded in place of the default FIRM (so, the SysNAND FIRM if you picked "Use SysNAND FIRM as default", and vice-versa).
• In order for AuReiNand to handle FIRM reboots, the .bin path needs to be hardcoded in the program. The default is /arm9loaderhax.bin (the AuReiNand.dat is also supported for 9.0 people). A PC tool was written to make changing the path easier. Compiled versions are provided for Windows, Linux and Mac OS. On Windows just drag the ARN .bin on top of the program, and write the path. On the other OSes you need to use the tool from a command prompt. If you have AuReiNand as randomloader/default.bin, just type: randomloader/default.bin.
• You can now use online for games even on outdated firmwares thanks to a patch by TuxSH. NVer is still needed to access the eShop and NNID-related services.
• You can now have the console report itself as a developer unit, which enables additional debugging in ErrDisp and also allows you to run software for development 3DSes on retail consoles. Thanks to Steveice10 for this!
• Rewrote the configuration menu to allow for multiple choice options and not to print the whole menu on each button press.
• Added a region/language emulation feature, thanks to the hard work of TuxSH. Create a "locales" folder inside aurei, and one .txt for each game, with the title id of the game (look them up on 3dsdb.com). The txt must be exactly 6 characters long: 3 for the region ("JPN", "USA", "EUR", "AUS", "CHN", "KOR", "TWN"), a space, and two for the language ("JP", "EN", "FR", "DE", "IT", "ES", "ZH", "KO", "NL", "PT", "RU", "TW"). You can enable the feature globally in the config menu. This should also finally make DLCs for foreign games work.
• Added a New 3DS CPU patch, again thanks to TuxSH. This only has an effect on New 3DS consoles, and allows you to configure the CPU inside the config menu, the same way NTR does: Off disables the patch, and then you can choose to enable the higher clock for all games, or the extra L2 cache, or both.
• AuReiNand should automatically work with future New 3DS FIRMs as the key generation is now built-in.
• Countless minor bug fixes and optimizations.
• Heartfelt thanks to these people for this release: Gelex from #cakey who helped me debugging a very nasty bug in the early stages of development, and obviously TuxSH for all his work and Steveice10 for the UNITINFO patch. Also thanks to everyone who supports the project and helps fixing bugs.

v4.2

• Fixed ARM11 access to chainloaded payloads (like CakesFW).
• Made the memory operations faster, as they're now better optimized thanks to -O3 (thanks TuxSH!)
• Added TWL/AGB FIRM patching/SD loading for New and Old 3DS (thanks to mid-kid of CakesFW for the reboot patch revision, and to TuxSH/Steveice10/others who worked on the patches for making it possible!). Please note that if you're booting a 9.0/9.2 NAND with 9.0 FIRM the reboot patch can't be applied (to not screw up exploits), and so the patched AGB/TWL won't work. You can also optionally enable the original GBA boot screen in the config menu.
• Fixed the second emuNAND patched FIRM still getting created.
• Made L not needed to load most payloads. You can now launch these payloads: up.bin, down.bin, left.bin, right.bin, x.bin, y.bin with only the corresponding button, and select.bin and r.bin with L+SELECT and L+R respectively. default.bin is now launched with just START or if the the button's matching payload doesn't exist.
• Added the possibility to configure the brightness for the built-in screen init. This is valid for all the instances in which AuRei inits the screen (config menu, payloads, errors). The 4 levels are respectively level 5, 4, 3, 2 from the 3DS OS. Just use Up to get to it in the config menu and use A to toggle.
• Code cleaned up and made more readable.

v4.1

• EmuNAND is now detected almost instantly when the CFW configures itself, and if the user is attempting to load an EmuNAND and none is found, SysNAND and 9.6/10.x FIRM are forced, instead of displaying an error message. This also prevents the second EmuNAND patched FIRM (patched_firmware_em2.bin) from ever being created if no second EmuNAND exists.
• You can now access the config menu after a soft reboot by holding just SELECT.
• Removed the copying of SecureInfo_A to ctrnand/rw/sys/SecureInfo_C on NAND from 3ds_injector, as it was done on each boot and possibly caused a slowdown. You can easily do the copy with GodMode9.
• Fixed loading the alternate EmuNAND if 9.0 FIRM was set as default and the user had an updated SysNAND. For this, I had to remove support for the "b.bin" payload.
• Fixed the current NAND showing incorrectly in System Settings after boot options were forced.

v4.0.1

Reuploaded to fix crash on exiting GBA games

• To override the last used boot mode on soft reboot, you only need to press A if you want to boot to the default option. Holding L(+payload button)/R is enough for the other modes.
• Added version number to the config menu
• Replaced the memsearch algorithm with a faster one
• Integrated 3ds_injector from @yifanlu. This brings us region free and all the other FreeMultiPatcher patches. Other than that, you now have the possibility to display the currently booted NAND/FIRM in System Settings!
• Rewritten most code for the config menu. You now can navigate to the first/last options with left and right.
• You can now choose the 9.0 FIRM to be default in the config menu. This will essentially switch "no buttons" and L in both modes.
• You can now choose the second emuNAND to be default in the config menu. This will essentially switch "B is not pressed" and "B is pressed".
• When the second emuNAND is booted, it will persist like the other boot options on soft reboot
• Bugfixes

v3.14

(Pi release)?

• Simplified the patching code.
• Yet one memsearch less (should make FIRM patching even slightly faster).
• Fixed A+L override when boot options are forced (this was the only one which stopped working).
• Dual RedNAND support.

v3.13

• Due to requests, changed the payload chainloading to use L+R just for the default payload, and L+button for the other ones. The default will be loaded if the corresponding payload doesn't exist.
• Increased the brightness of the built-in screen init.
• Blocked Safe Mode (L+R+Up+A) access on A9LH, as using it would brick the console (N3DS) or remove A9LH due to the reboot to SAFE_MODE FIRM.

v3.12

• Introduced a configuration menu which can be called by holding SELECT on boot, which replaces "flags". It appears automatically when the config file is not found, and it can be used to toggle the options that were "flags" previously.
• AuReiNand now prints error messages before shutting down.
• To reduce SD card accesses and make the program more newbie friendly, emunand.bin, reboot.bin and loader.bin have been merged into the main executable.
• FIRM patching has been made slightly faster (only applies if pre-patched FIRMs aren't used) by removing two memory searches.
• AuReiNand will auto-delete the pre-patched FIRMs when you switch to/from A9LH or, in the future, new FIRM patches are added.
• Payload chainloading now also works from CakeBrah.

I'd like to thank mid-kid at CakesFW for the screen printing code :)