binary-io: Attempted use of O_BINARY on consoles no longer fails.
Reported by KO Myung-Hun <komh78@gmail.com> in
<https://lists.gnu.org/archive/html/bug-gnulib/2019-05/msg00124.html>.
* lib/binary-io.h (__gl_setmode_check): Remove function.
(set_binary_mode): Declare as notinline on DJGPP and EMX.
* lib/binary-io.c (__gl_setmode_check): Remove function.
(set_binary_mode): Define here on DJGPP and EMX. Inline
__gl_setmode_check. In case of a tty, don't return an error code.