Merge branch 'hv/mingw-fs-funnies'

* hv/mingw-fs-funnies: mingw_rmdir: set errno=ENOTEMPTY when appropriate mingw: add fallback for rmdir in case directory is in use mingw: make failures to unlink or move raise a question mingw: work around irregular failures of unlink on windows mingw: move unlink wrapper to mingw.c