Make Special:TrackingCategories fully detect namespace switching

Special:TrackingCategories has special logic to detect people
using {{NAMESPACE}} in their tracking category messages, and
handle it. Make it detect any '{{' to deal with localized
variants. This will make it work for
[[commons:MediaWiki:Broken-file-category]]

Change-Id: Ibac0decc5992d30ae536efc91138ad9b42a569e9