swift234

[Coverage] Do not move PGO name pointers into __llvm_prf_names

Instead, pass name pointers to InstrProfiling::lowerCoverageData() using
the new API (via getCoverageUnusedNamesVarName). This ensures that we
don't emit an uncompressed *and* a compressed version of all function
names into the module, fixing rdar://problem/25493310.

(cherry picked from commit 668d81f1f34b49f98c2d9bf0eb6d58d0c248f70e)