Fix NSEdoc generation problems due to block ordering

Reported here: http://seclists.org/nmap-dev/2014/q2/258

Complicated parsing issue, but short version is this: The NSEdoc for
scripts must not be followed by a local declaration, or it will not be
accepted. Easiest way is to be sure the block with @usage, @output,
@args, @xmloutput, etc. comes right before the author line.