Midi support

[hvolkmer]

This adds support for midi controllers. Tested using a Behringer CMD LC-1 controller.

Midi events can be mapped (input device support) using lmc_set_midi_handler and notes can be sent to the controller (to e.g. set LEDs) via lmc_send_midi_note.

I will add more error handling (verifying device types, checking if devices are still there) but wanted to create this request to get some feedback.

I usually don't write Pascal code, so let me know if any coding or naming conventions are off. I tried to stick to the style that was already in the code. Let me know if should change anything.

This addresses #2

[me2d13]

Thanks for pull request. Why were you changing uKbdDeviceService? I suppose you have difficulties to compile it but si I have with your changes. Seeing the explicit uRawInput. reference you have added you had multiple decalrations e.g. of PRAWINPUT?
One of the compilation errors I have now is call of GetRawInputDeviceList where you added @ (as address) to 2nd parameter. But the declaration of GetRawInputDeviceList I have in uRawInput unit has this parameter as var so the reference is passed by compiler, you dont need (and can't use) pointer - that's my compile error.
What's the FPC/Lazarus version you have used?

[hvolkmer]

I used Lazarus 1.8.2 FPC 3.0.4 (the current available latest download from the website).

I basically just looked at the history and saw that this code was changed back and forth a at least once and basically reversed the last change. That made it compile and it also seems to work.

This change is obviously totally unrelated to my addition and I'd rather not have it in here at all, but it was necessary to compile. I am not sure what to do here. I'd be happy to remove/change it in any way as long as everything still works.