maint: revert gnulib update, until fixed automake is in more distros

The previous commit (56f34e55) accidentally bumped to latest gnulib,
but that adds a syntax check for CVE-2012-3386 that won't be fixed
until Automake 1.11.6/1.12.2 lands in more distros.

* .gnulib: Undo accidental commit.

.gnulib @ a02ba4bf

-Subproject commit 48fe477c9008efadab8cf8c0c3240d824c12a8b9
+Subproject commit a02ba4bf889fee4622db87f185c3d0af84d74ae7