applet.audio.yamaha_opx: add streaming timeout. Otherwise people would glitch it and wait for something to happen while holding the synthesizer lock.

applet.audio.yamaha_{opl→opx}: add OPM support.

applet.audio.yamaha_opl: add wait states after soft reset.

applet.audio.yamaha_opl: add stereo support.

applet.audio.yamaha_opl: move resampling to client side. This gives better results latency-wise, could (in principle; not currently implemented) handle context sample rate changing during playback (which WebKit can apparently do), and also makes downloaded WAV files true to the original PCM data.

applet.audio.yamaha_opl: update doc. NFC.

applet.interface.uart: remove `tty --cr`. It looks like the default mode (no --cr) only ever works by accident, so let's get rid of it instead. (But maybe I'm wrong? Unix TTY is not my strong point.)

applet.audio.yamaha_opl: fix mounting at a path.

aplet.audio.yamaha_opl: raise chunk size. Chunk size being too low has caused latency issues.

applet.audio.yamaha_opl: fix minor frontend issues.