maint: update to latest gnulib

maint: update to latest gnulib

Future patches need LGPLv2+ versions of some modules that had
recent license changes; but separating the gnulib update from
the actual use of the modules makes it easier to backport to
an older version while avoiding a submodule update (assuming,
of course, that the backport is to a system where glibc provides
adequate functionaliy without needing the gnulib module).

* .gnulib: Update to latest, for modules needed in later patches.

Signed-off-by: Eric Blake <eblake@redhat.com>