Add PPC test for r227481, but XFAIL because this is actually more work than it appeared to be.

Same sort of bug as on ARM where the cmp+branch are lowered to br_cc
(choosing the branch's debugloc for the br_cc's debugloc) then expanded
out to a cmp and a br, but both using the debug loc of the br_cc, thus
losing fidelity.

llvm-svn: 227645