glw: Use float constants
Minor work on Web UI
rpi: Default goal should be stripped version
Makefile: Add some tiny helpers for building profiling builds
Remove unused crap in accelerated video codecs init
Rework how codecs are created

We now defer the initialization of some audio codecs to the
audio decoder thread. This allows us to, based on the audio output
configuration, ask the codec to do downmixing by itself

Also fix so DVD playback can use HW accelerated codecs
DVD: Use buffered I/O
skin: Change notification layout
Rework thread priorities

We now have much more fine grained priorities.

Set priority on Linux use setpriority() after spawning thread.

Complain on Raspberry Pi if we are not granted realtime scheduling
httpclient: Improve keep-alive handling a lot

Better retry logic if we fail when using a reused connection.

Also adhere to the "Keep-Alive: timeout=N" HTTP header
rpi: Always downmix to stereo for now
glw: Add reduced CPU mode

This mode (currently only used on RPi) reduces CPU usage at expense
of an UI that's sometimes slower to update