Encapsulating the playSound call

It's kind of a drag to have to write that stupid ((CPopApp*)::AfxGetApp())->. all the time. Assuming that it's normally a cCritter that's going to make a call to make a sound, try adding a cCritter::playSound(CString soundname) method to the cCritter class. Let the method do the tedious fetching of CPopApp and also let it stick in the standard flags SND_RESOURCE | SND_ASYNC as one of the arguments. Using this new method, add code to have the asteroids in the spacewar game make a little noise when they collide. Think of more sounds to add, too