handle 2.3 - 2.4 git upgrades better

[shish]

if the config file isn't moved, there's no "you need to move the config file" message, just "PHP Notice: Use of undefined constant DEBUG_SQL - assumed 'DEBUG_SQL' in /var/www/main/projects/p/core/util.inc.php on line 467"

[jgen]

Thanks Shish.

I didn't realize the config file had changed / moved. If its not possible to upgrade the file then perhaps notifying the use like you said would be a good idea.