Removed all macro code for PIC (goodbye "la").
Support tested with shootout bench.

llvm-svn: 43697

- Added a function to hold the stack location 
  where GP must be stored during LowerCALL
- AsmPrinter now emits directives based on
  relocation type
- PIC_ set to default relocation type (same as GCC)

llvm-svn: 42779

llvm-svn: 41525

llvm-svn: 39758