*** Implement frame pointer elimination on X86!

* Include contents of X86RegisterClasses.cpp into here
* Adjustments to register api to work with new frame manager
* Eliminate moveImm2Reg, getFramePointer, and getStackPointer
* Cleanup and simplify prolog/epilog code generation
* Prolog/epilog are MUCH more efficient now.

llvm-svn: 5186