Use unaligned stores to save XMM regs to stack.

On Win32, the stack isn't aligned, so aligned stores will cause crashes.
Compute stack usage correctly in ABI_CallFunctionPC.

(The numbers need to be consistent with the actual usage, or else the stack gets corrupted.)
Save registers before calls in x86-32 JIT.

I have no idea what the person who added RegistersInUse() was thinking,
but not correctly saving registers is an easy way to end up with crashes.
Merge pull request #211 from magumagu/win32-jit-fixes

Win32 jit fixes