Adding edge case of MIDI mapping for Ableton Push

[Replayman]

Hi,
This is a little code update to take into account another edge case of MIDI in / MIDI out controller with different mappings.

As of today, I wasn't able to deploy a working dev and build environment to verify compilation of MIXXX with this update (harder under Windows...) but here is it anyway as this is only a few lines of code.

[Replayman]

Here is the developer log at MIXXX startup for these 2 devices:

Debug [Controller]: Scanning PortMIDI devices:
Debug [Controller]: Found output device # 0 Microsoft MIDI Mapper
Debug [Controller]: Found output device # 3 Microsoft GS Wavetable Synth
Debug [Controller]: Found output device # 4 Ableton Push
Debug [Main]: BaseTrackPlayerImpl::slotLoadTrack "[Sampler1]" QObject(0x0)
Debug [Controller]: Found output device # 5 MIDIOUT2 (Ableton Push)
Debug [Controller]: Found input device # 1 Ableton Push
Debug [Controller]: Linking to output device # 4 "Ableton Push"
Debug [Controller]: Found input device # 2 MIDIIN2 (Ableton Push)
Debug [Controller]: Scanning HSS1394 devices:
Debug [Controller]: Nodes detected: 0
Debug [Controller]: Scanning HID devices:

[daschuer]

Even though I cannot test this, the changes are looking reasonable.

[daschuer]

Thank you very much for your fist contribution.
Before merge, we need your permission.
Please sign https://docs.google.com/a/mixxx.org/spreadsheet/viewform?formkey=dEpYN2NkVEFnWWQzbkFfM0ZYYUZ5X2c6MQ
and comment here when done.

[Replayman]

Thank you very much for your fist contribution. Before merge, we need your permission. Please sign https://docs.google.com/a/mixxx.org/spreadsheet/viewform?formkey=dEpYN2NkVEFnWWQzbkFfM0ZYYUZ5X2c6MQ and comment here when done.

Signed, thank you.

[daschuer]

Thank you! I like to add your name to the contributor list in the Mixxx About Box. Should I use your GitHub User name or your real name?

[Replayman]

Thank you! I like to add your name to the contributor list in the Mixxx About Box. Should I use your GitHub User name or your real name?

My real name please, thank you!