In an effort to reduce the likelihood of text getting out of sync, reusing the...

In an effort to reduce the likelihood of text getting out of sync, reusing the text from some diagnostics explicitly. No functional changes intended.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198078 91177308-0d34-0410-b5e6-96231b3b80d8