Win32 updates to physfs.

[Ryan C. Gordon]

First, VisualC.zip has been removed from the CVS repository. There's no
need to bloat the download with this unnecessarily for non-win32 users, so
it's been moved to http://icculus.org/physfs/downloads/physfs-win32-support.zip

That zipfile should be used with both Visual C and Cygwin.

Second, win32.c's __PHYSFS_platformRealPath() has been rewritten (albeit
in a somewhat ugly fashion), and compiles on both Cygwin and Visual C. The
only thing now preventing a total Cygwin build is the lack of support in
the Makefile (most of it is there, actually; I just don't know how to tell
Cygwin to build a DLL).

Unrelated to win32:
I got Mandrake installed on my iMac, and after a quick test found that
PhysicsFS compiles clean out of the box for Linux on the PowerPC. The only
place where there is likely to be a byte-ordering issue will be the GRP
archive support, and even there it's unlikely. I'll have to experiment
some more, though.

Up next:
- Figure out how to determine if a disc is "mounted" on win32.
- Add byte-independent read/write functions (PHYFS_readInt32(), etc).
- CodeWarrior build on MacOS 9.

--ryan.