[Development report #40] Audio Stack Improvements

snd_hda: Fix a sporadic panic during kldunload:
https://reviews.freebsd.org/D50393

	- Further discussion.

sound: Merge pcm_sysinit() with pcm_register():
https://cgit.freebsd.org/src/commit/?id=a946852ff2963b5ec83cb7ccb5eee214b1d47ad5

sound: Terminate stream properly when closing vchans:
https://cgit.freebsd.org/src/commit/?id=f6430bc61df78be070209d52b4452ae9cf4cd015

	- Also MFC'd to stable/14 and releng/14.3.

snd_dummy: Make callout stopping more robust:
https://cgit.freebsd.org/src/commit/?id=0432b2183f25ddba7e13a33adf1dd6f9563b0bd1

	- Also MFC'd to stable/14.

virtual_oss: Exit main loop cleanly on termination:
https://github.com/freebsd/virtual_oss/commit/7b833e492e6ab1f112c0f5a88a3c767abc391485

virtual_oss: Clean up cuse on exit:
https://github.com/freebsd/virtual_oss/commit/a0860ca4972c473578c8025d8d0cf400aafaa724

virtual_oss: Clean up pthread on exit:
https://github.com/freebsd/virtual_oss/commit/fcf3d0e7d1e3b351975f444606ba30d1e5106fbf

virtual_oss: Start service after ldconfig:
https://github.com/freebsd/virtual_oss/commit/5f390b09cab09cc276d532dbe691ee234a37a531

audio/virtual_oss: Start service after ldconfig:
https://cgit.freebsd.org/ports/commit/?id=7b5548779bb1a5e86c2a340ebab352e685e018d6

	- Fixes PR 287198:
	  https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=287198

sound: Deprecate the MIDI sequencer:
https://cgit.freebsd.org/src/commit/?id=799105f53a9647f86dbf08456260d5850851b6f9

	- Also MFC'd to stable/14.

sound: Retire the MIDI sequencer:
https://reviews.freebsd.org/D50605

sound: Retire midisynth:
https://reviews.freebsd.org/D50609

sound: Retire /dev/midistat:
https://reviews.freebsd.org/D50610

sound: Retire unused MIDI sysctls:
https://reviews.freebsd.org/D50611

sound: Remove unused mpu_if methods:
https://reviews.freebsd.org/D50612

sound: Remove duplicate mpu_if.h include:
https://reviews.freebsd.org/D50613

sound: Remove unnecessary comments from midi/midi.c:
https://reviews.freebsd.org/D50615

sound: Remove unused midi_cmdname():
https://reviews.freebsd.org/D50616

sound: Remove dead printfs from midi/mpu401.c:
https://reviews.freebsd.org/D50617

PR 222636:
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=222636

Started working on BSDCan presentation.

Technical support emails with users.

This work is sponsored by the FreeBSD Foundation.

Christos