[OpenMP] libomp cleanup: add checks of bad memory access

Add check of frm to prevent array out-of-bound access;
add check of new_nproc to prevent access of unallocated hot_teams array;
add check of location info pointer to prevent NULL dereference;
add check of d_tn pointer to prevent NULL dereference in release build.
These checks make static analyzers happier.

This is second part of the patch from https://reviews.llvm.org/D84062.