[PATCH] Gear, brake and handbrake sounds

[MirceaKitsune]

Worked on implementing some ear candy today. Added sounds for changing gears (you hear a discrete click when the gear is changed), brake sound (you hear the brake pedal and mechanism when you brake) and handbrake sound.

TODO: Make the sounds per car, not global, so different cars can have different versions of these sounds. I couldn't figure how to use the carpath + carname shortcuts with the way I implemented it. For now they work as global sounds though.

Sound files taken from OpenGameArt. Gear sound, brake sound, handbrake sound. Yeah, those sounds were made for completely different purposes, but I felt they work for the cars until better ones are found All seem to be GPL compatible.

Patch download locations: link 1, link 2. Hope this is good to commit and that someone can fix the car paths so they can be per-car