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/unpwdb.lua

@@ -134,8 +134,9 @@ table_iterator = function(table)
   end
 end
 
---- Returns the suggested number of seconds to attempt a brute force attack,
--- based on the <code>unpwdb.timelimit</code> script argument, Nmap's timing
+--- Returns the suggested number of seconds to attempt a brute force attack
+--
+-- Based on the <code>unpwdb.timelimit</code> script argument, Nmap's timing
 -- values (<code>-T4</code> etc.) and whether or not a user-defined list is
 -- used.
 --
@@ -209,9 +210,10 @@ local passwords_raw = function()
   return true, table_iterator(passtable)
 end
 
---- Wraps time and count limits around an iterator. When either limit expires,
--- starts returning <code>nil</code>. Calling the iterator with an argument of
--- "reset" resets the count.
+--- Wraps time and count limits around an iterator.
+--
+-- When either limit expires, starts returning <code>nil</code>. Calling the
+-- iterator with an argument of "reset" resets the count.
 -- @param time_limit Time limit in seconds. Use 0 or <code>nil</code> for no limit.
 -- @param count_limit Count limit in seconds. Use 0 or <code>nil</code> for no limit.
 -- @return boolean Status.