The audio_file classes (wav, ogg, opus) represent audio files.

- audio_file is an abstract base class that holds the audio data and info.

- each derived class loads the data in its constructor.

- currently the old code is used for the loading.
Audio file factory

The audio_file_factory class has one static method that returns a
std::unique_ptr<audio> that points to a wav_file, ogg_file or
opus file depending on the extension of the provided filename.
Changed the name of bit_depth to byte_depth

The name was changed because bit_depth was inaccurate.
The value is the actual bytes.
Audio file returns const pointer

Changed the void pointer that is returned by audio_file.get_audio_data()
to const void.
Remove MusicSound

Since the file system does not support partially loading a file
MusicSound does not have any uses. Its functionality is now
part of LoopingSound.
Remove the audio_file hierarchy

Removed the audio_file (and {wav,ogg,opus}_file} in favor of a simpler
AudioData struct, which contains the relevant audio data. Reduce the
audio_file_factory to functions that return AudioData objects.
Update CMakeLists.txt
AudioData now deletes any memory it owns.

If rawSamples* is owned by an AudioData object, it will be deleted
during destruction, this is the case for loaded audio files.

Also, a few ugly casts were removed.
Initial work on implementing the filesystem in the vm
Add comparison operator to AudioData
Fix typo
Change all #ifdefs to use the new BUILD_* target macros
Move the filesystem compatibility wrapper to qcommon
Implement the new wav loader.

WavCodec uses engine/framework/Filesystem to read the audio files.

All the relevant data is returned in a AudioData struct.

In case of an error an empty AudioData is returned.
Improve deps package generation, resolve symlinks on windows platforms
Use zip for deps on windows
Clean up a lot of warnings and improve compile flags a bit
Build the nacl gamecode in travis
Download a more recent version of cmake on travis
Use a pre-built version of CMake on travis