JIT64: optimize carry calculations

Omit carry calculations that get overwritten later in the block before they're
used. Very common in the case of srawix and friends.
JIT64: optimize carry calculations further

Keep carry flags in the x86 flags register if used in the next instruction.
PPCAnalyst: refactor, add carry op reordering and non-cmp reordering

Tries as hard as possible to push carry-using operations (like addc and adde)
next to each other. Refactor the instruction reordering to be more flexible
and allow multiple passes.

353 -> 192 x86 instructions on a carry-heavy code block in Pokemon Puzzle.
12% faster overall in Pokemon Puzzle; probably less in typical games (Virtual
Console games seem to be carry-heavy for some reason; maybe a different
compiler?)
PPCAnalyst/JIT: add ability to easily toggle branch and carry merging