maint: update to latest gnulib

While this update doesn't address any reported problems in libvirt,
doing a post-release update to latest gnulib makes it easier to
stay in sync with best upstream practices.

* .gnulib: Update to latest.
* bootstrap: Resynchronize.

bootstrap

@@ -1,6 +1,6 @@
 #! /bin/sh
 # Print a version string.
-scriptversion=2013-01-20.16; # UTC
+scriptversion=2013-03-08.16; # UTC
 
 # Bootstrap this package from checked-out sources.
 
@@ -630,9 +630,13 @@ esac
 if $bootstrap_sync; then
   cmp -s "$0" "$GNULIB_SRCDIR/build-aux/bootstrap" || {
     echo "$0: updating bootstrap and restarting..."
+    case $(sh -c 'echo "$1"' -- a) in
+      a) ignored=--;;
+      *) ignored=ignored;;
+    esac
     exec sh -c \
       'cp "$1" "$2" && shift && exec "${CONFIG_SHELL-/bin/sh}" "$@"' \
-      -- "$GNULIB_SRCDIR/build-aux/bootstrap" \
+      $ignored "$GNULIB_SRCDIR/build-aux/bootstrap" \
       "$0" "$@" --no-bootstrap-sync
   }
 fi