[OPENMP50]Allow functions in declare variant directive to have different
C linkage.

After some discussion with OpenMP developers, it was decided that the
functions with the different C linkage can be used in declare variant
directive.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@374057 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed