Fix a problem on Windows machines with >32 processors

git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@217024 91177308-0d34-0410-b5e6-96231b3b80d8
Fix a bug where the library slept for up to KMP_BLOCKTIME before exiting

git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@217026 91177308-0d34-0410-b5e6-96231b3b80d8
Fix a crash that occurred under obscure circumstances during library shutdown

git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@217027 91177308-0d34-0410-b5e6-96231b3b80d8