Merge r18689:r19511 from /nmap-exp/djalal/nse-rules.

o Add two new Script scan phases:
  Script Pre-scanning phase: before any Nmap scan operation, activated by the new "prerule".
  Script Post-scanning phase: after all Nmap scan operations, activated by the new "postrule".
o New environment variables:
  SCRIPT_PATH
  SCRIPT_NAME
  SCRIPT_TYPE: the type of the rule that activated the script.

scripts/http-favicon.nse

@@ -57,7 +57,8 @@ action = function(host, port)
   end
 
   if not pcall(require,'openssl') then
-	stdnse.print_debug( 3, "Skipping %s script because OpenSSL is missing.", filename )
+	stdnse.print_debug( 3, "Skipping %s script because OpenSSL is missing.",
+	    SCRIPT_NAME)
 	return
   end