maint: update to latest gnulib

Another update is required to pick up today's gnulib fix for mingw
builds (now that gnulib turns on mingw's replacement printf that
understands %lld, it must also tell the compiler to respect the
improved definition of PRIdMAX and friends).

* .gnulib: Update to latest.
Signed-off-by: NEric Blake <eblake@redhat.com>

.gnulib @ c27f1a35

-Subproject commit 498a1b6bc7d70f944ca0f939e1bc470889fdce76
+Subproject commit c27f1a356f2f321daa7f971ef276a1dbfa873bf8