OpenMPClause.h: Fix a warning. [-Wdocumentation]

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@220266 91177308-0d34-0410-b5e6-96231b3b80d8
Update documentation to match API change in r215323.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@220267 91177308-0d34-0410-b5e6-96231b3b80d8
Add missing qualifier to documentation.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@220268 91177308-0d34-0410-b5e6-96231b3b80d8