[ut3] Linux Server and AMD Athlon 2600 dual processor

[Ryan C. Gordon]

> It's because the Athlon processors you are using do not support the SSE2 
> instruction set that the UT3 server demo requires. Ryan mentioned this 
> shortly after the demo was released. See the mailing list archive for 
> more info.

This is fixed for retail. A _lot_ of people wrote in to say they didn't 
have SSE2 support, so I reduced compiler optimizations.

--ryan.