Modifications so we can compile with G++.

Corrected compilation differences between G++ and VS, mostly with respect to
exception handling. G++ wants SDLException to be properly defined, whereas
VS accepts a foreward declaration; G++ wants uniform signatures, whereas VS
doesn't care if you don't include throw( SDLException ) in the .cpp.

Also, included "dummy" Resource.cpp. G++ won't compile unless it exists; VS
doesn't care.