- Update register allocation hint after coalescing. This is done by the target...

- Update register allocation hint after coalescing. This is done by the target since the hint is target dependent. This is important for ARM register pair hints.
- Register allocator should resolve the second part of the hint (register number) before passing it to the target since it knows virtual register to physical register mapping.
- More fixes to get ARM load / store double word working.

llvm-svn: 73671