* fixes "~winpthreads changes ~pthread_signal.h" etc. reported by build-pkg
mingw-w64 installs dummy headers if winpthreads isn't built
* enables libgomp to avoid double-build (see #331)
* no change in openmp-validation (still 20 failures - taken with a grain of
salt as the batch file test runner isn't a reliable perl substitute)
* pthreads virtual package kept for future testing
Tony Theodore
Timothy Gu
Fernando Ortiz