Reapply debug info changes now that more precise column information is available.

(recommitting as the Clang patch is back in with the latest fix -
hopefully it sticks)

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@225001 91177308-0d34-0410-b5e6-96231b3b80d8
[asan] add flag coverage_pcs. When false, the coverage is not dumped as PCs. Useful e.g. if the user only needs coverage is bitset

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@225002 91177308-0d34-0410-b5e6-96231b3b80d8