[clang-tidy] A new OpenMP module

Summary:
Just the empty skeleton.
Previously reviewed as part of D57113.

Reviewers: JonasToth, aaron.ballman, alexfh, xazax.hun, hokein, gribozavr

Reviewed By: JonasToth, gribozavr

Subscribers: jdoerfert, mgorny, rnkovacs, guansong, arphaman, cfe-commits

Tags: #clang-tools-extra, #openmp, #clang

Differential Revision: https://reviews.llvm.org/D57571

llvm-svn: 356800