[OpenMP][bugfix] Add missing math functions variants for log and abs.
Summary: When including the random header in C++, some of the math functions it relies on are not present in the CUDA headers. We include this variants in this case.
Reviewers: jdoerfert, hfinkel, tra, caomhin
Reviewed By: tra
Subscribers: efriedma, guansong, cfe-commits
Differential Revision: https://reviews.llvm.org/D62046