Tomaz patch to fopen builtin which now tries to read files outside data/ (but won...

Tomaz patch to fopen builtin which now tries to read files outside data/ (but won't try to write or append outside data/), for better compatibility with other engines that don't use data/ in their FRIK_FILE implementation

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@4181 d7cf8633-e32d-0410-b094-e92efae38249