Should Emacs 26 be portable to Glibc 2.28?

[Paul Eggert]

-#if defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Haiku, Linux libc5 */
+#if defined _IO_ftrylockfile || defined _IO_EOF_SEEN || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Haiku, Linux libc5 */

Thanks, good suggestion, I installed that into Gnulib[1] and copied it
into Emacs master[2].

However, after looking into this some more it turns out that we need not
backport it to emacs-26. For Emacs built with Glibc, fpending.c is
compiled only for glibc 2.1.92 and older, which means that the
portability bug with glibc 2.28 cannot be triggered for Emacs. Sorry
about the false alarm.

[1]
https://git.savannah.gnu.org/cgit/gnulib.git/commit/?id=74d9d6a293d7462dea8f83e7fc5ac792e956a0ad

[2]
https://git.savannah.gnu.org/cgit/emacs.git/commit/?id=f0c590b857415e94a8ed9ded0e9ba2f91ea2a3c7