Move PhysFS functions into PhysfsUtil and rely on PhysFSUtil more

[tobbi]

We have a wild mix between using physfsutil for tasks and raw PHYSFS_-prefixed functions.

It would be great if all the relevant functions could be moved into physfsutil. That makes it much easier in case of API changes because we only need to update the relevant parts in the PhysfsUtil class.

As PhysFS is moving beyond 2.0 into 3.0 territory with API changes...well...

[Vankata453]

Most times I've looked at parts of the code that perform PhysFS operations, I have thought the same... physfsutil should be more widely used as a wrapper throughout the source indeed.