Comment 1 for bug 1606335

Took a while until I found the proper workaround there
http://www.mixxx.org/wiki/doku.php/midi_scripting#available_common_functions
> script.midiPitch(LSB, MSB, status)

Mapped pitch slider to this function in MyController.js:
TerminalMix.pitchSlider = function (channel, control, value, status, group) {
    engine.setValue(group,"rate",-script.midiPitch(control, value, status));
}