Reapply "[SimplifyCFG] In sinkLastInstruction correctly set debugloc of common inst"

This reapplies r289828 (reverted in r289833 as it broke the address sanitizer).  The
debugloc is now only set when the instruction is not a call, as this causes the
verifier to assert (the inliner requires an inlinable callsite to have a debug loc
if the caller and callee have debug info).

Original commit message:

Simplify CFG will try to sink the last instruction in a series of basic blocks,
creating a "common" instruction in the successor block (sinkLastInstruction).
When it does this, the debug location of the single instruction should be the
merged debug locations of the commoned instructions.

Original review: https://reviews.llvm.org/D27590

llvm-svn: 290973