linux_caller_save() doesn't match ABI

[bchurchill]

I don't want to break anything, so I won't change this function quite yet. The name of these function doesn't quite match up to what they are though: linux_caller_save() currently returns the list of all registers used as parameters; however, the caller must also save rax, r9, r10 and r11, which aren't parameters.

I also have a really hard time with the names callee/caller save, but that's probably just me, so my current solution is to define four new additional functions:
linux_call_parameters()
linux_call_scratch()
linux_call_preserved()
linux_call_return() (including rax, rdx, xmm0, xmm1)

that return the appropriate sets of registers.

[bchurchill]

Merged into develop only.