build: update to latest gnulib, for syntax-check

This picks up a fix for a syntax-check weakness mentioned here:
https://www.redhat.com/archives/libvir-list/2013-May/msg00811.html

* .gnulib: Update to latest, for maint.mk improvement.

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

diff --git a/.gnulib b/.gnulib
index 0f8ddbf1a13a93a4584afdd82f0f87e498a0db6f..a363f4ed4a0e69187c97686ac44502c49c7f4b3d 160000 (submodule)
--- a/.gnulib
+++ b/.gnulib
@@ -1 +1 @@
-Subproject commit 0f8ddbf1a13a93a4584afdd82f0f87e498a0db6f
+Subproject commit a363f4ed4a0e69187c97686ac44502c49c7f4b3d