* external.cc (sync_wincwd): Remove.

	* external.cc (sync_wincwd): Remove.
	(cygwin_internal): Drop CW_SYNC_WINCWD case.
	* globals.cc (ro_u_pipedir): New R/O unicode string.
	* ntdll.h (RtlSetCurrentDirectory_U): Declare.
	* path.cc (cwdstuff::set): Improve comments.  Drop setting Win32 CWD to
	\\?\PIPE\ on init.  Keep Win32 CWD in sync, if possible.  Set to
	\\?\PIPE\ otherwise.
	* include/cygwin/version.h (CYGWIN_VERSION_API_MINOR): Revert to 230.
	* include/sys/cygwin.h (cygwin_getinfo_types): Remove CW_SYNC_WINCWD.