[OpenMP] Adding GOMP compatible cancellation

Remove fatal error messages from the cancellation API for GOMP
Add __kmp_barrier_gomp_cancel() to implement cancellation of parallel regions.
This new function uses the linear barrier algorithm with a cancellable
nonsleepable wait loop.

Differential Revision: https://reviews.llvm.org/D57969


git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@354367 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed