[openal] Repository of OpenAL extensions on GitHub

[OpenAL Ext]

Hi,

since there was no universal (and up to date) repository of OpenAL extensions, I've decided to compile information available from different sources and create a GitHub repository to store them. As for now, a lot of these descriptions are only stubs or extracts from headers.

Github project is available at
https://github.com/openalext/openalext

Hope you find it useful.