Make notifications_content.module aware of localized content type names

Patch updated: the block of notifications_content.module needs another go: it used the already-mentioned notifications_tt(), which I considered to be wrong (see the arguments above), thus replaced to tt().

If we are checking the availability of i18nstrings.module, we cannot be sure that the content type names gets translated (eg. even the "nodetype" textgroup may be unavailable). If we are checking i18content.module instead, the "nodetype" textgroup does exist, so we may have a better chance that the proper translations are available. Anyway, I don't know how a textgroup gets deleted - so if one enabled i18ncontent.module, translated the content type names (and descriptions), and disabled i18ncontent.module (but left i18nstrings.module enabled), the proper translations may remain available, which means it's quite enough to check the availability of tt() (ie. i18nstrings.module). On the other hand I cannot see a way to translate the content type names (and descriptions) besides using i18ncontent.module (by the means of the UI).

Correct me if I totally misunderstood something - I'm quite new to this area. If I'm convinced about the opposite (ie. that blindly using notifications_tt() is the way to go), I'll gladly reroll the patch.

Am I right that the functionality of the above patch has been already committed (and part of 2.2), at least partially? If yes, what happened to the second hunk? I don't quite seem to find how node type names and descriptions get translated. :S