Backport to 4.6

Couldn't figure out where else to put this, so here goes...

Needed a 4.6 version of gotwo.module for a 4.6 site implementation. Ended up doing the following:

• Backported forms from 4.7 API to 4.6 style.
• Added 'gotwo url' permission for access control to redirected resources. (Don't ask, but basically, we prevent a user from going to an external link unless they're a member...)
• Patched to redirect for external URL's, since drupal_goto does not handle in 4.6

Works for us, but use at your own risk.