for tw/twi instructions, force propagated constant into a register to avoid "a1 cannot be immediate" errors from the emitter
Fix twi/tw instructions being switched in Jit64 and JitArm; downgrade the ERROR_LOG printed when tw is ran in the interpreter to DEBUG
JIT: fix a corner case in crXXX

It didn't behave correctly with an input of zero, resulting in some games
breaking (at the least, Fight Night 2). This should be fixed now.

Also clean it up, add a few comments, and fix some variants of the instruction
that are so rare that they probably never got tested.
Rename Log2 and add IsPow2 to MathUtils for future use

Also remove unused pow2/pow2f functions.
JIT64: optimize multiplication by immediate constants

Factor out common code and handle a few more common cases.
JIT64: optimize rlwinmx/rlwinix and friends

Take advantage of movzx as a replacement for anding with 0xff or 0xffff, and
abuse loads from the register cache to save ops.
JIT64: Optimize cmpXX

Use TEST instead of CMP if we're comparing against 0 (rather common), and
optimize the case of immediate compares further.
JIT64: optimize sign-extend

Remove some code duplication.

Also remove some comments that no longer apply since x86_32 was dropped.
JIT64: avoid using LEA for adds when not necessary
JIT64: use LEA for the "a = b + imm" case of addi
JIT64: tweak srwx/slwx BindToRegister arguments

Register B gets immediately moved into the shift register, so even if a == b
it doesn't need to be loaded.
JIT64: optimize carry handling

Carries are rather common and unpredictable, so do them branchlessly wherever
we can.
JIT64: optimize some special cases of srawix

Shift by 31 and 1, both of which are pretty common, can be done in a few less
instructions. Tested with a hwtest.
JIT64: support merged branching for rlwinmx, too

Not quite as common a branch instruction as cmpwi, but close.
Common: Fix code styling in Arm64Emitter
Merge pull request #1044 from lioncash/pedantry

Common: Fix code styling in Arm64Emitter
Merge pull request #1017 from zhuowei/tw_fallback_if_constant_ra

Fix various issues with the twi/tw instructions
Merge pull request #1035 from FioraAeterna/fixcrxxx

JIT: fix a corner case in crXXX
Merge pull request #753 from FioraAeterna/integeropts

JIT64: various integer optimizations