* syscalls.cc (open): Only return ENOTDIR if file exists.
	* libc/base64.c: New file.
	* Makefile.in (DLL_OFILES): Add base64.o.
	* common.din: Export __b64_ntop and __b64_pton.
	* posix.sgml (std-bsd): Add __b64_ntop and __b64_pton.
	* include/cygwin/version.h (CYGWIN_VERSION_API_MINOR): Bump.
	* new-features.sgml (ov-new1.7.19): Add __b64_ntop and __b64_pton.