Separate the serialization library's diagnostics from the frontend's
diagnostics. Conflating them was highly confusing and makes it harder to
establish a firm layering separation between these two libraries.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@146207 91177308-0d34-0410-b5e6-96231b3b80d8
9 files changed