code mangling update...

[Ryan C. Gordon]

I've just wrapped up a round of source code mangling...a lot of
reworking I've been wanting to do for awhile is done.

1) Archiver interface is much simpler
2) Less allocations and junk
3) Less complexity in physfs.c

The diffs are nasty, but I think it was worth it...the code is at least
a little less intimidating to the uninitiated now.  :)

I also changed PHYSFS_file to PHYSFS_File, since it didn't match the
rest of the API's naming convention. Don't worry, there's a typedef in
physfs.h for legacy source, so nothing should break.

Please pound on this and report crashes. A lot of it was cleaning up
void pointers named "opaque" to other void pointers named "opaque", so
I'm sure there'll be _something_ that compiled cleanly but ends up
pointing at a structure of the wrong datatype.  :)

--ryan.