[physfs] Making PHYSFS_FILETYPE_* a bitmask

[Ryan C. Gordon]

> So in the case a symlink that points to a file filetype would be set to
> PHYSFS_FILETYPE_REGULAR|PHYSFS_FILETYPE_SYMLINK.

The original intention was to match what most OSes do: you get the entry 
from the filesystem, and if you want to resolve the symlink it reports, 
you have to do more filesystem accesses.

However: what do we set this to if the symlink is pointing to another 
symlink? If we resolve all the symlinks, what do we set this to if the 
final symlink points back to the first, causing an infinite loop? What 
do we set this to if it's not pointing to anything at all?

Granted, we don't offer a PHYSFS_readlink() API to report to the app 
what a symlink points to, and we probably should.

--ryan.