*added a fallback sr in case everything else fails

*fixed regression where audio properties misreported sampling rate

*updated most of the audio API to the latest version (with the exception of ALSA and JACK which are partial until our improvements can be merged and/or new implementation of JACK thoroughly tested to ensure we like its default behavior)

*experimental commit that makes sample rate work properly in -nogui mode by leveraging requested audio_rate in case current sample rate is uninitialized

reverted 0.43 backport as its implementation seems unstable when trying to (re)connect to jack via audio properties. Fixed a bug where closing jack while having DAC on would hang pd.

backported audio driver support from 0.43 and the pd/extra folder with supporting fixes/merges where needed. Removed outdated expr-help file in favor of new documentation.