re PR bootstrap/79771 (in-tree zlib breaks build)

2017-03-15  Yaakov Selkowitz <yselkowitz@redhat.com>

	PR bootstrap/79771
	* gzguts.h (WIDECHAR): Do not define for __CYGWIN__.
	* zlib.h (gzopen_w): Do not declare for __CYGWIN__.
	* win32/zlib.def: Remove gzopen_w.

From-SVN: r246152