vtxdec: small omission
Merge pull request #4479 from unknownbrackets/perf

Small optimizations (armjit) for imms
Add comment with link to important github thread about sceSas threading
armjit: Preserve imms on min/max as well.
armjit: optimize reverse subtract, avoid temp imms.

If we have a non-op2 imm, get rid of it asap.  If we have a op2 friendly
imm, keep it.
armjit: Improve GPR typesafety.
armjit: Allocate regs in preferred slots.

This may allow better flushing.  Not sure if these are the best regs,
but if they aren't it shouldn't really hurt.
armjit: Flush regs using STMIA where possible.