Support of mips & mips64 for openmprtl

Summary:
Implemented by Dejan Latinovic
See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=790735 for more more information

Reviewers: AndreyChurbanov, jlpeyton

Subscribers: openmp-commits, mgorny

Differential Revision: https://reviews.llvm.org/D26576

git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@289032 91177308-0d34-0410-b5e6-96231b3b80d8