[OpenMP] Eliminate some compiler warnings

* Remove accidental == for =
* Assign values to variables to appease compiler
* Surround debug code with KMP_DEBUG
* Remove unused local typedefs

Differential Revision: https://reviews.llvm.org/D60983


git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@359599 91177308-0d34-0410-b5e6-96231b3b80d8