[mythtv] CPU detection/optimization

[Chris Petersen]

> BTW -mfpmath=sse gives approximately a 10-20% speed boost to MythTV
> depending on various factors.

So does this get printed in, then?  I was wondering why there was a flag 
for mmx but not sse.  would love to be able to do both (if it's not 
there already), esp. with flags so that I can actually build some 
optimized packages for other archs.

-Chris