physfs-2.0.2 update formula to build out of source, and specify
-DPHYSFS_BUILD_TEST=TRUE so that we compile a cli named test_physfs
that lets you interactively operate on supported archives
(e.g. Quake II PAKs or DOOM WADs). There were no problems with
64bit OSX 10.6.8 with gcc, llvm, or clang from XCode 4.0.2.
ClosesHomebrew/homebrew#8273.
Signed-off-by: Charlie Sharpsteen <source@sharpsteen.net>