* binmode.c (cygwin_premain0): Don't use underscore'd variants of the
	open flags.
	* textmode.c (cygwin_premain0): Ditto.
	* include/fcntl.h: Move all open flags (except O_NDELAY) to newlib's
	sys/_default_fcntl.h.
	* libc/include/sys/_default_fcntl.h: Move all Cygwin-specific open
	flags from Cygwin's fcntl.h here.  Remove check for WIN32.  Remove
	Windows-specific macros.
	* libc/include/sys/_default_fcntl.h: Move all Cygwin-specific open
	flags from Cygwin's fcntl.h here.  Remove check for WIN32.  Remove
	Windows-specific macros.