Yet another NP_Trackback hack
I've got an email from my host administrator to warn me that one of my MySQL table consumed lots of system load, and the table is nucleus_trackback.
But I haven't got any "real" trackbacks, so they are all spams, and more accurate, crazy spams, that simply too much to overload my DB.
So I have to wrote this patch to add an option to NP_Trackback: drop blocked trackbacks directly. After enabled, trackbacks that blocked by NP_Trackback (failed spam test or no link) will not be stored into the DB.