Basic/Diagnostics: Add a DiagnosticMappingInfo helper class, and switch to
storing mappings with that instead of straying some magic constants about the
source.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@140760 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed