When file status is unknown, don't set O_CREAT when opening read-only.

2013-11-15  Janne Blomqvist  <jb@gcc.gnu.org>
	    Jerry DeLisle  <jvdelisle@gcc.gnu.org>

	PR fortran/59108
	* io/unix.c (regular_file): Don't set O_CREAT when opening a file
	read-only with unknown status. Mask out O_CREAT when falling back
	to opening read-only if ACTION= is not set and read-write fails.

Co-Authored-By: Jerry DeLisle <jvdelisle@gcc.gnu.org>

From-SVN: r204864