Save mute automation state.
Factor out duplicated track automation code.

Mute automation for MIDI tracks.
Clean up state tracking of raw MIDI.
Add missing namespace qualifiers.
Move EventRingBuffer to libardour.

This is not used anywhere in Evoral and is just a wrapper around the PBD
RingBuffer anyway.  Towards a (once again?) independently buildable/testable
Evoral and fewer cross-dependencies.
Trim the include tree.
Fix test runner for tests that use files.
Remove bogus test and noisy output.
Remove dead code.
Replace thinning static state with parameter.
Remove braindead Parameter inheritance abuse.