[Mediawiki-api] Breaking change: cmnamespace parameter disabled

[Carl (CBM)]

The 'cmnamespace' parameter to the 'categorymembers' query has been
disabled in miser mode, which has the effect of disabling it on WMF
wikis. The parameter is simply ignored, causing category lists to
include pages in all namespaces. The simplest workaround is to filter
category lists locally.

References:
* http://www.mediawiki.org/wiki/Special:Code/MediaWiki/53052
* https://bugzilla.wikimedia.org/show_bug.cgi?id=19640

- Carl