remote-mediawiki: show progress while fetching namespaces

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:

https://github.com/Git-Mediawiki/Git-Mediawiki/issues/30

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