[mythtv] CPU detection/optimization

[Chris Petersen]

> You can use --extra-cflags --extra-cxx-flags to change the compilation
> options. However, please do not distribute these binaries unless you
> tell the people downloading them to go to you for bug reports. If you
> distribute these binaries, the people using them will probably not
> know to recompile with standard options and confirming that the bug
> exists in that build.

well, rpm likes to add its own compile options for things like arch, so 
the idea would be to have standard stuff to conform to the rest of 
redhat/fedora.

As far as things like sse, if they make a difference and they're 
autodetected with p4/athlon/etc, I'm cool with that, too.

My main concern is to have a package that conforms to the preferred 
standards for fedora/redhat (what those are is somewhat up for debate at 
the moment, due to some political stuff, but we'll work through that). 
Beyond that, I plan to add a --autodetect-cpu type flag to let the 
configure script do its thing -- and will suggest that people use it, 
since it'll give them better results than a binary compiled for a more 
generalized setup.

-Chris