Fix warnings and 64-bit issues in pthread testcases. See pthread-win32 commit 1183e5ac etc.
project. * winsup.api/pthread/cancel2.c: Ditto. * winsup.api/pthread/cancel3.c: Ditto. * winsup.api/pthread/cancel4.c: Ditto. * winsup.api/pthread/cancel5.c: Ditto.