OpenAL SDK updated to support newer PureBasic versions

The PureBasic OpenAL SDK was updated. It is now hosted here, as a sub-project under ImpLib SDK. The source code is mirrored to GitHub.

What's new:

• The new version is compatible with PureBasic (32-bit) up to v6.10 LTS. Version 6.11 introduces a new linker (lld-link) which doesn't currently support the OpenAL SDK library format.
• The UserLib source code is included into the delivery, which can be useful to recompile the library for compatibility with a specific PureBasic version.
• Some optimizations in the source code to reduce the size of the User-Lib.

The new version is available for download here.