Pause flag used inconsistently in GameClock

```
What steps will reproduce the problem?
The GameClock class is initialized with the flag self.paused, and
self.paused is checked in update(), but the pause() and unpause() functions
use the flag self.pause. 

Changing all of these to self.paused fixes the issue.
```

Original issue reported on code.google.com by `bcorfman1@gmail.com` on 22 Jan 2008 at 2:10
