NSEdoc cleanup

Mostly splitting function summaries (the first paragraph of NSEdoc) from
the body of the description to make the summary indexes shorter and
easier to scan.

Also fixed some unbalanced code tags like <code>foo</table>

nselib/ssh2.lua

@@ -39,7 +39,8 @@ check_packet_length = function( buffer )
 end
 
 --- Receives a complete SSH packet, even if fragmented
---  this function is an abstraction layer to deal with
+--
+--  This function is an abstraction layer to deal with
 --  checking the packet size to know if there is any more
 --  data to receive.
 --