[OPENMP] Initial parsing and sema analysis for 'taskwait' directive.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@213363 91177308-0d34-0410-b5e6-96231b3b80d8
ARM: Add test for ACLE memory barrier intrinsics

Add an additional test to ensure that someone doesn't accidentally
change the definitions such that they can take a non-constant value.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@213364 91177308-0d34-0410-b5e6-96231b3b80d8