Introduce 'framebuffer' SPEC variable to distinguish hardware framebuffer drivers furthermore from the SDL framebuffer driver used by Genode/Linux.
OSS driver, ALSA driver, audio-out test, avplay, and mixer Issue #602
With this patch the SDL-based 'avplay' media player, which is part of 'libav', can be built. The run script expects a media file named 'mediafile' in the 'bin' directory. Fixes #216.