Added some asserts to the pluralized power message functions.
Added some asserts to the pluralized power message functions.

mazaclub/mazabot-core,haxwithaxe/supybot,Ban3/Limnoria,kblin/supybot-gsoc,ProgVal/Limnoria-test,mazaclub/mazabot-core,ProgVal/Limnoria-test,prashantpawar/supybot-rothbot,Ban3/Limnoria,raboof/supybot,buildbot/supybot,jeffmahoney/supybot,frumiousbandersnatch/supybot-code