Use a static fixed point libopus build to improve audio performance

Limelight-embedded currently uses the libopus.so present on the system. The problem with this is that libopus has implemented significant decoding performance improvements in 1.0 and later that aren't present on (at least) Rasbian wheezy which uses libopus 0.9. In addition, this static lib is built with the --enable-fixed-point option which allows use of ARM assembly and media extensions to improve performance further. Using a single libopus build will prevent distro-specific differences related to the versions of libopus present.

I've included a build here, but if you'd like to build libopus.a for yourself, checkout git://git.opus-codec.org/opus.git then run ./autogen.sh (requires autoconf and libtool), then run ./configure --enable-fixed-point

I'm measuring CPU usage with top on my Pi in game without touching any input devices. With audio completely disabled in master, I see about 20% CPU usage. With master without my changes, I see about 50% CPU usage. With my changes in master, I see 37% CPU usage.