remove superfluous stuff.

* arp
* dhcpc
* mdns-sd
* sntp
* ptp
* tuio1
* scsynth
* dummy
* custom
* ipv4ll
add missing break in switch statement.
fix compilation with gcc-11.
update build status link in REAME.
update gitlab ci recipe.
extend gitlab ci recipe.
prototype gitlab ci recipe.
fix sensor number range in OSC API.
get rid of INFINITY min/max ranges in OSC API.
set default MIDI controller to SC1 (0x46) for MPE.
update travis recipe.
dump firmware version in releasor.
support 'b'lob type output for oscmidi engine.
imporove SLIP encoding.

* do double SLIP encoding according to OSC-1.1 spec.
* use short-cut for more efficient encoding.
fix wrong module value.
implement MIDI MPE mode in oscmidi engine.