[physfs] 2.0.2 Documentation

[Ryan C. Gordon]

> Thanks, it makes docs compile, though they are compiled in the main root and
> are not installed with make install. I'll use the root instead of an external
> directory, thanks a lot.

Latest in revision control now properly builds the documentation in the 
right place for out-of-tree builds. Hooking this up to "make install" 
turned out to be basically impossible unless I want the documentation to 
be forced to build (and frankly, I really dislike Doxygen's manpage 
generation, so it's honestly better if this doesn't install by default).

--ryan.