Merge current work back to tree to minimize diffs and drift. Major highlights

for CellSPU modifications:

- SPUInstrInfo.td refactoring: "multiclass" really is _your_ friend.
- Other improvements based on refactoring effort in SPUISelLowering.cpp,
  esp. in SPUISelLowering::PerformDAGCombine(), where zero amount shifts and
  rotates are now eliminiated, other scalar-to-vector-to-scalar silliness
  is also eliminated.
- 64-bit operations are being implemented, _muldi3.c gcc runtime now
  compiles and generates the right code. More work still needs to be done.

llvm-svn: 47532