Move engine/client/{qal|snd}* to engine/audio
Client: remove dependencies to audio/snd_local.h
Remove the in house sound mixer implementation
Add dummy trap calls to update an entity velocity and occlusion for the audio system
Fix the syscalls
Merge branch 'master' into engine-upgrade/sound
Remove QAL and use openAL directly
Audio: simplify the OpenAL includes
Audio: remove VoIP and platforms specific hacks

VoIP will be reintroduced and platforms specific hacks will
hopefully not be needed if we use OpenAL Soft everywhere
Audio: WIP on the rewrite.

* Introduce ALObjects: a minimal wrapper to hide OpenAL calls
* Introduce Samples: load raw samples from files (= buffer)
* Broken
  * Streaming audio (VoIP and maybe something else)
  * Buffers are not freed (=> no handling of memory pressure evnets)
  * Can only compile with VoIP off
  * Ambients loops are not synchronized
  * Entity loops restart the loop after leave-entering the maxDist
Audio: WIP on the rewrite:

* Introduce Sounds: the description of a sound (one shot, looping, music, streamed, with added reverb...)
* Introduce Emitters: where the sound is played and what positional effects to add.
* Broken
 * There is a small "tick" at the end of the sample in the menu not sure why
 * Removed music for now
 * Removed looping sounds for now
Fix travis build?
Fix travis build (disable tty-client by default for now)
Audio WIP on the rewrite:

* Introduce the audio API file that will be the new snd_public
Audio WIP on the rewrite:

* Ownerships changed a little between Sound and Emitter
* Emitters get a Sound to update instead of a Source (will be useful when we have shaders)
Audio WIP on the rewrite:

* Introduce loops back
* Remove most of the code in snd_openal.c so as to not have interferences
Audio WIP on the rewrite:

* Make a private audio header because I'm lazy
* API -> Audio to have <module>/<Module>.h for the API
Audio: Reuse shared_ptr's reference counting for Emitters
Cvar: add support for float cvars
Audio: add support for volume cvars

Also contains a fix for some loops having a popping sound when they stop
abruptly: we find out the sound slowly, for now in a framerate dependant
way :(
Not sure if we should kep this or rely on mappers to not make sounds too
loud and popping.