fix: automatic coupler crashes, horns, compressor start delay, radio and cab lever sounds

- automatic couplers don't catch above the safe collision speed (#86): with crash damage on they couple at a
  closing speed of 15 km/h at most, a faster hit locks the coupling until the vehicles part and the collision
  runs its course. On the way: CollisionVelocity() read a head-on 10 + 10 km/h as 14.1 km/h (quaternions turn
  by half the angle), it's now taken from the touching ends; CollisionDetect() took the other vehicle's speed
  the wrong way round for vehicles facing each other. Head-on hits now derail sooner, at the intended limit,
- a single horn lever can't sound both tones at once (eu07/maszyna#392),
- a skid ends once the vehicle stops on locked wheels (eu07/maszyna#479),
- electronic destination signs are blanked at the end of the timetable (eu07/maszyna#446),
- horns need the air or the voltage to sound (eu07/maszyna#290, #76): HornType=[Pneumatic]|Electric and
  Horn3Type in Cntrl.; a pneumatic horn needs 0.2 MPa in the main reservoir (or the main pipe without one),
  an electric one the low voltage; the lever stays where it was put,
- compressor start delay (#67): CompressorStartDelay [s] in Brake., counted from the compressor getting its
  power, after the engine starts say; none by default,
- the channel and volume buttons of a radio without power do nothing (eu07/maszyna#429); the power check of
  the radio is TMoverParameters::RadioPowered(),
- a lever moved smoothly sounds the positions it passes (#83).

Sonar findings in the functions changed: nesting, nested conditionals, commented-out code, std::format,
references to const. Unit tests: test::pair for two vehicles running into each other, test_couplers,
test_horn, test_wheelslip, test_compressor, test_radio, test_gauge_positions.

vehicle/horn.cpp

@@ -0,0 +1,24 @@
+/*
+This Source Code Form is subject to the
+terms of the Mozilla Public License, v.
+2.0. If a copy of the MPL was not
+distributed with this file, You can
+obtain one at
+http://mozilla.org/MPL/2.0/.
+*/
+
+#include "stdafx.h"
+#include "vehicle/horn.h"
+
+namespace horn {
+
+int pressed(int const Signal, int const Tone, bool const Singlelever) {
+	auto const other{Tone == low ? high : low};
+	return (Signal | Tone) & (Singlelever ? ~other : ~0);
+}
+
+int released(int const Signal, int const Tone) {
+	return Signal & ~Tone;
+}
+
+} // namespace horn