compatibility with destination

I would like to have the following feature:

1) anonymouse users try to view a page of some restricted content type.
2) some module (e.g. r4032login) redirects anonymous users to user/login.
3) ip_login shows the login link if the ip address matches the range.
4) autholized users by ip_login are redirected to the page which the user tried to view in (1).

The attached patch may resolve the issue in this scenario. The patch works as follows:

1) save the destination url in the session (_SESSION) if the destination (_GET) is given for user/login.
2) call drupal_goto with the saved destination, in ip_login_attempt_login().

Please note that the final destination is over written if other module (for example, login_destination) is enabled.

Moreover, drupal_get_destination() may be more suitable for this purpose. In this patch, since I'm not so sure about the query variable "q", I dare to use a direct way to get the destination.