Gosu::Sample panning and speed broken under mojoAL

[cyberarm]

I only noticed this when trying to change a samples playback speed for my game jam project... 😞

[jlnr]

At a first glance I would have thought that this Google result must have made its way into mojoAL by now -> https://twitter.com/icculus/status/1297383424731369472

Thanks for reporting. AL_PITCH is one of my favorite Gosu features, so I might take a look at it in the future.

[cyberarm]

It seems to work fine on Windows... 🤔 More debugging I guess. 🙃

[jlnr]

Panning works on macOS, but pitch doesn't.

[jlnr]

Re AL_PITCH: icculus/mojoAL#2

I have updated mojoAL here to see if it works #625