[OpenMP] Implement 5.0 memory management

* Replace HBWMALLOC API with more general MEMKIND API, new functions
  and variables added.
* Have libmemkind.so loaded when accessible.
* Redirect memspaces to default one except for high bandwidth which
  is processed separately.
* Ignore some allocator traits e.g., sync_hint, access, pinned, while
  others are processed normally e.g., alignment, pool_size, fallback,
  fb_data, partition.
* Add tests for memory management

Patch by Andrey Churbanov

Differential Revision: https://reviews.llvm.org/D59783

llvm-svn: 357929