diagnostic from the emission of macro backtraces. Incidentally, we now get the
displayed source location for a diagnostic and the location for the caret from
the same place, rather than computing them separately. No functionality change.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@169357 91177308-0d34-0410-b5e6-96231b3b80d8