Fix Launchpad X detection on macOS

[frankgrimy]

As stated on #13633, Mixxx wasn't configuring Novation Launchpad X correctly, because of a name mismatch between its input and output interfaces in macOS.

[daschuer]

The code looks good, thank you. The is just a stray white space character reported by pre-commit.
This can even go to our stable 2.4 branch.
Can you rebase this to 2.4? If you have a local working copy, you may:
git reset upstream/2.4 --hard
git cherry-pick 81d1a8406ec
git push -f
Than use the edit feature above to change the merge target.

I'm addition we need you permission to distribute your changes along with Mixxx.
Please sign: https://docs.google.com/a/mixxx.org/spreadsheet/viewform?formkey=dEpYN2NkVEFnWWQzbkFfM0ZYYUZ5X2c6MQ

And comment here when done.

[frankgrimy]

Well, it seems ok now. I've also signed the form.

[daschuer]

Cool. Thank you. I would like to add you to the contributor list in the Mixxx about box. Which name should I use?

[frankgrimy]

Just go with Frank Grimy

[Swiftb0y]

I'm a little too late, but an alternative solution would be change the other heuristic code instead of stripping input and output, we should just strip in and out.

[daschuer]

It is hard to predict property naming conventions anyway. I think a better solution would be to make this part of the mappings. Something like collecting this matching table from all found mapping files.