audio/alsa-plugins: convert options to subpackages

[jbeich]

Summary

Avoid heavy pulseaudio dependency by default. Trivial case: no USE* and no subpackage consumers (everything wants only OSS plugin).

Test Plan

Runtime tested inside jail via aplay.

$ poudriere testport -j 132amd64 audio/alsa-plugins
[...]
=>> Checking shared library dependencies
 0x0000000000000001 NEEDED               Shared library: [libasound.so.2]
 0x0000000000000001 NEEDED               Shared library: [libc.so.7]
 0x0000000000000001 NEEDED               Shared library: [libthr.so.3]

$ poudriere testport -j 132amd64 audio/alsa-plugins~ffmpeg
[...]
=>> Checking shared library dependencies
 0x0000000000000001 NEEDED               Shared library: [libasound.so.2]
 0x0000000000000001 NEEDED               Shared library: [libavcodec.so.60]
 0x0000000000000001 NEEDED               Shared library: [libavutil.so.58]
 0x0000000000000001 NEEDED               Shared library: [libc.so.7]
 0x0000000000000001 NEEDED               Shared library: [libswresample.so.4]

$ poudriere testport -j 132amd64 audio/alsa-plugins~jack
[...]
=>> Checking shared library dependencies
 0x0000000000000001 NEEDED               Shared library: [libasound.so.2]
 0x0000000000000001 NEEDED               Shared library: [libc.so.7]
 0x0000000000000001 NEEDED               Shared library: [libjack.so.0]
 0x0000000000000001 NEEDED               Shared library: [libthr.so.3]

$ poudriere testport -j 132amd64 audio/alsa-plugins~pulseaudio
[...]
=>> Checking shared library dependencies
 0x0000000000000001 NEEDED               Shared library: [libasound.so.2]
 0x0000000000000001 NEEDED               Shared library: [libc.so.7]
 0x0000000000000001 NEEDED               Shared library: [libpulse.so.0]
 0x0000000000000001 NEEDED               Shared library: [libthr.so.3]

$ poudriere testport -j 132amd64 audio/alsa-plugins~samplerate
[...]
=>> Checking shared library dependencies
 0x0000000000000001 NEEDED               Shared library: [libasound.so.2]
 0x0000000000000001 NEEDED               Shared library: [libc.so.7]
 0x0000000000000001 NEEDED               Shared library: [libsamplerate.so.0]

$ poudriere testport -j 132amd64 audio/alsa-plugins~speex
[...]
=>> Checking shared library dependencies
 0x0000000000000001 NEEDED               Shared library: [libasound.so.2]
 0x0000000000000001 NEEDED               Shared library: [libc.so.7]
 0x0000000000000001 NEEDED               Shared library: [libspeexdsp.so.1]

[jbeich]

• Rebase after c402d06aa792
• Add SELF_DEPENDS.<subpkg>=main due to libasound.so.2 (see NEEDED)
• Add pkg-descr.<subpkg> as suggested in D43576

[jbeich]

• Revert SELF_DEPENDS as libasound.so is part of alsa-lib, not alsa-plugins

[jbeich]

• Move one more file to jack subpackage (missed during 609ec25809c7 rebase)
• Lowercase plugin names in pkg-descr.<subpkg>

[jbeich]

• Rebase after 14b194a6952f
• Depend on alsa-lib in subpackages
• Tested alsa-plugins-jack runtime via pcm.!default pcm.plug:jack in asound.conf

[mat]

This seems ok, if you have actually tested things still work after the conversion, go ahead.