Combine multiple roles and account for the increase in total paths used

This may be of use to others too:

For a clients site we needed to extend path_access to combine the paths of all roles assigned to a user instead of just using the last one from the standard query. Worked so far, but yesterday we apparently exceeded a php regexpr limit beause of the dramaticly increase in total paths for user with lots of roles.

Solution was simple: just take the unique paths.

Cause of the "our live site is giving errors!!!!" part I was in a hurry, but I think the result isn't too bad. So hope this gets into trunk. Combining roles makes more sense to me then to just 'take' one anyway, perhaps this should at least be a variable?

Patch is for current stable 1.0 for drupal 6