Issue #3 fix

Comments.php - changes for "comments" and "trackbacks"
en_US.pl - changed: Keyword list - for _n support
added - nplurals forms
changed stuff for ../comments.php [7,10,11 lines]
unfortunatly - all .po files have to be rebuild as this en_US to get this update. example in pl_PL.po and en_US.po