Support generating machine instructions for Phi nodes (based on x86, but with

modifications for 1 LLVM BB --> many MBBs).
Fix store operand order: make it always be Base, Offset, SrcReg (think
"[ Base + Offset ] = SrcReg").
Rewrite visitBranchInst() to be even dumber (but working) -- give up on
the branch fallthrough trick, for the time being.
Make visitSetCondInst() work.

llvm-svn: 14208