[OpenMP] Fix issue with directives used in a macro.
Summary:
If directives are used in a macro, clang complains with:
```
src/projects/openmp/runtime/src/kmp_runtime.c:7486:2: error: embedding a directive within macro arguments has undefined behavior [-Werror,-Wembedded-directive]
#if KMP_USE_MONITOR
```
This patch fixes two occurrences of the issue in `kmp_runtime.cpp`.
Reviewers: tlwilmar, jlpeyton, AndreyChurbanov, Hahnfeld
Subscribers: Hahnfeld, openmp-commits
Differential Revision: https://reviews.llvm.org/D25823
llvm-svn: 284728