Fix Splash module so page caching can be enabled and it doesn't display the Splash page every time. Note, this disables caching on the homepage. Not ideal, but still better than it used to be.

Issue #320067 by sirkitree, Make sure Splash actually doesn't display when the Never (off) option is selected in the settings

Issue #1296698 by jimappleg8: Ensure $_GET['splash'] is set before trying to check its value to eliminate undefined index errors.

Miscellaneous code cleanup to adhere to Drupal coding standards (http://drupal.org/coding-standards).