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/mysql-databases.nse

@@ -35,7 +35,8 @@ dependencies = {"mysql-brute", "mysql-empty-password"}
 if not pcall(require,"openssl") then
 	portrule = function() return false end
   	action = function() end
-  	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