Current mesa expects stdio.h to prototype fileno() when compiling with gcc
-std=c99 -D_XOPEN_SOURCE
Fix the 'POSIX 1003.1:2001' block in stdio.h to prototype functions if not
__STRICT_ANSI__, or _BSD_SOURCE, _POSIX_C_SOURCE or _XOPEN_SOURCE are defined
appropriately
As far as I can tell, despite being in this block, setbuffer() and setlinebuf()
are BSDisms which aren't in POSIX 1003.1:2001
Signed-off-by: Jon Turney <jon.turney@dronecode.org.uk>
c5fee55606