ptsname_r: Fix test failures on IRIX, Solaris.

* m4/ptsname_r.m4 (gl_PREREQ_PTSNAME_R): Test whether isatty sets
errno when it fails. Define ISATTY_FAILS_WITHOUT_SETTING_ERRNO
accordingly.
* lib/ptsname_r.c: Include <fcntl.h>.
(__ptsname_r): When isatty returned false, then on IRIX, Solaris
set errno if fd is invalid.
* tests/test-isatty.c (main): Update comments.

1 files changed, 2 insertions, 2 deletions

diff --git a/tests/test-isatty.c b/tests/test-isatty.c
index 263e05ed04..195a9066b9 100644
--- a/tests/test-isatty.c
+++ b/tests/test-isatty.c
@@ -45,14 +45,14 @@ main (void)
     errno = 0;
     ASSERT (isatty (-1) == 0);
     ASSERT (errno == EBADF
-            || errno == 0 /* seen on Solaris 10 */
+            || errno == 0 /* seen on IRIX 6.5, Solaris 10 */
            );
   }
   {
     errno = 0;
     ASSERT (isatty (99) == 0);
     ASSERT (errno == EBADF
-            || errno == 0 /* seen on Solaris 10 */
+            || errno == 0 /* seen on IRIX 6.5, Solaris 10 */
            );
   }