* PHP:

- Now use "proc_open()" when "popen()" is not available.

* Other:

- Fixed a typo that broke download functionality.
- It is now possible to force file saving and deletion, even if
PRS think that file can not saved or deleted.
- PRS is now able of self-modify itself to save dynamic data in
its own file. If it fail (ie. bad PRS file rights) it use
traditional cookie method.
- Safer read/write file functions.
- Code cleaning and minor enhancements.