Forward progress: crtbegin.c now compiles successfully!

Fixed CellSPU's A-form (local store) address mode, so that all globals,
externals, constant pool and jump table symbols are now wrapped within
a SPUISD::AFormAddr pseudo-instruction. This now identifies all local
store memory addresses, although it requires a bit of legerdemain during
instruction selection to properly select loads to and stores from local
store, properly generating "LQA" instructions.

Also added mul_ops.ll test harness for exercising integer multiplication.

llvm-svn: 46142