with -Werror.  Previously, compiling with -Werror would emit only the first
warning in a compilation unit, because clang assumes that once an error occurs,
further analysis is unlikely to return valid results.  However, warnings that
have been upgraded to errors should not be treated as "errors" in this sense.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@169649 91177308-0d34-0410-b5e6-96231b3b80d8