potx 6.x-2.0

New feature: Coder (http://drupal.org/project/coder) integration support, so you can do code reviews with translation errors as well
API change: potx status reporting API changed

Fixed bugs and got the 5.x and 6.x parser in line:

- #205100 by phirdina: plural translations were missing in exported po files due to bugos database logic
- Forward porting the Unknown file version handler from 5.x
- Getting potx-6.1 and 6.2 in sync:
   - updated documentation to match actual behaviour (folding, tab title)
   - some code style changes from the 6.1 version
   - ported region name and default user role detection from 6.1
   - ported duplication marking for installer strings in runtime export from 6.1
- #213801 report by nancyw, patch by myself: replace old permission name with new one

This is going to be the supported branch later on.