remote-mediawiki: show progress while fetching namespaces

Without this, the fetch process seems hanged while we fetch page
listings across the namespaces. Obviously, it should be possible to
silence this with -q, but that's an issue already present everywhere
in the code and should be fixed separately:

Git-Mediawiki/Git-Mediawiki#30

Signed-off-by: Antoine Beaupré <anarcat@debian.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/mw-to-git/git-remote-mediawiki.perl

@@ -279,6 +279,7 @@ sub get_mw_tracked_namespaces {
             aplimit => 'max' } )
             || die $mediawiki->{error}->{code} . ': '
                 . $mediawiki->{error}->{details} . "\n";
+        print {*STDERR} "$#{$mw_pages} found in namespace $local_namespace ($namespace_id)\n";
         foreach my $page (@{$mw_pages}) {
             $pages->{$page->{title}} = $page;
         }