headers: Add missing include guards in pathcch.h
github: build and test winpthreads library
winpthreads: Regenerate Makefile.in
winpthreads: Skip the pthreads_exit/exit1 testcase
winpthreads: enable warnings when compiling tests
winpthreads: correctly print time_t values in pthread_rwlock/rwlock{7,8}.c
winpthreads: avoid warnings about comparison between integers and pointers in tests
winpthreads: fix compilation of some tests with recent gcc