Summary:
Change the test in isAllowedClauseForDirective from if with multiple conditions
to a main switch on directive and then switches on clause for each directive. Version
check is still done with a condition in the return statment.
Reviewers: jdoerfert, jdenny
Reviewed By: jdenny
Subscribers: yaxunl, guansong, sstefan1, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D83363