Fix input in configuration tool (SDL2)

[maron2000]

While you can edit your settings using Configuration Tool, the characters you see when you type with Shift-key was messy.
This is due to that SDL2 provides correct keycode if Shift-key is NOT pressed, but provide incorrect keycode if Shift is pressed.
As a result, you find some keys not possible to type with a non-US keyboard.

This PR will make all keys act as US keyboards for the time being so that at least you can type all common symbols.
We can further fix this if we can find out a way that SDL2 will provide the keycode when Shift-key is pressed.
Also, keypad keys were not working, so made it work.

Test result on JP keyboard
Before fix
Shift+1,2,3 is !@#, as same as US keyboard.
Shift+P,@,[ is P@{ which is not correct. (Shift+@ is not @)

After fix
P,@,[ on JP keyboard is P,[,]
Shift+ P,@,[ is P,{, }