Major changes in PhysFS, plus some exception fixing.

Major changes in PhysFS, plus some exception fixing.

PhysFS now have a new structure. PhysFS (the class) became a
namespace. RWopsFromFile became a simple function in namespace PhysFS, IStream,
Ostream, IStreambuf, OStreambuf are classes in PhysFS namespace. The remaining
functions are now in a class called Manager inside PhysFS. The class is fully
static, so no more need to PhysFS::instance->Stuff(), simply
PhysFS::Manager::Stuff(). Also a set of PhysFS exceptions invented, and most
functions throw exceptions, so don't forget to write exception handler, if you
need it! Also, I've added a lot of documentation, so have a look at the Doxygen
documentation for more info.

I've also included a library, ProtectStr to access C-style strings safely. It's
dual licensed (GPL, WTFPL) because I think, it's so basic and useful, that
other projects could use it too, without limitations..