Add MIDI clock source

[Benjamin Klum]

No description provided.

[Benjamin Klum]

re #100 Add MIDI clock source first draft

→ <<cset fb7000d56fea>>

[Benjamin Klum]

re #100 Improve MIDI clock a bit but still draft

→ <<cset 06cfa3247713>>

[Benjamin Klum]

re #100 Fix parsing of non-integer bpm values

→ <<cset 032139838185>>

[Benjamin Klum]

re #100 Allow to set MIDI input device for MIDI clock source

→ <<cset 3fb8cc128e8c>>

[Benjamin Klum]

re #100 Introduce MIDI clock transport source and fix audio dropout

... when opening UI

→ <<cset d7b9d4037f5d>>

[Benjamin Klum]

re #100 Only observe global MIDI events if at least one MIDI clock source

Also fix potential crash and slightly improve performance.

→ <<cset b4a18aba73eb>>

[Benjamin Klum]

MIDI clock tempo source is in a purely experimental state, more a proof of concept than a rock-solid implementation. Maybe it will be improved in future. I think for many use cases syncing REAPER tempo to MIDI clock is not the best tempo-adjustment method anyway.