Covering 128-bits of address space with immediates and labels

[fwsGonzo]

Right now there are special pseudo-instructions meant to help with:

1. Loading large integer into register
2. Loading large addresses into register
3. Calling large address using JALR by building address in register

These helpful functions right now cover only 32-bits of address space, however they should cover up to 128-bits. It's a bit hard to see right now how this should be done without using a lot of unnecessary registers.

One note about the farcall instruction is that it avoids loading the integer, because it uses the immedate of the JALR instruction to build the 32-bit value, saving an instruction.

If nothing else, maybe we can solve this by just adding la64 and la128 variants that assume you know the distance is great.

[fwsGonzo]

For now there is the set pseudo-instruction which uses an intermediate register to build large constants.