This patch implements atomic intrinsics atomic.load.add (sub,and,or,xor,

nand), atomic.swap and atomic.cmp.swap, all in i8, i16 and i32 versions.
The intrinsics are implemented by creating pseudo-instructions, which are
then expanded in the method MipsTargetLowering::EmitInstrWithCustomInserter.

Patch by Sasa Stankovic.

llvm-svn: 132323