Keep the stack aligned when tripping memchecks.
Save regs before/after 3-arg func calls on x86.

This fixes bugs only on x64 when ABI_CallFunctionACC and etc. were used.
This was breaking things since R8 was not being saved (arg 3.)
Re-enable lwl/lwr/swl/swr on the x86 jit.

Now correctly handling ECX on x64.
Don't rewind the PC on memcheck w/ CORE_NEXTFRAME.

If the memcheck doesn't hit, we'll still rewind the PC, causing weirdness.
This is likely if you try to memcheck an address hit first thing in a
vblank interrupt handler or something.
Merge pull request #2647 from unknownbrackets/jit-minor

Fix x64 jit bugs (memchecks and lwl/lwr/swl/swr)