Allow running discourse with prefix with passenger without requiring a symlink

This allows running the application with a prefix without requiring a symlink in Apache htdocs. This does not affect running in thin.

This is done by BitNami (as we require it to allow changing prefix) and does not affect non-prefix stacks in anyway. We want to make as little changes to discourse that are not in the discourse repository as possible - therefore we to include it so we do not have to apply the patch.