[physfs] physfs tutorial

[Ryan C. Gordon]

> *cough*
> 
> ".\\..\\..\\respacks\\built\\TestTheme\\theme.tff"

Yes, that's what I meant.

Note that in test_physfs, it's not escaped, though.

There was discussion about making Cygwin builds use '/' as a path
seperator to make them "Unix-like", but I'm not sure I think that's
right for gamers

--ryan.