Drop Jack x42/weakapi

[Snowiiii]

Enhancement Summary

Currently we are using x42's WeakAPI to load the Jack library, We should move to the Official API

Implementation Details / Mockup

The Official API can be found here

Please search the issue tracker for existing feature requests before submitting your own.

• I have searched all existing issues and confirmed that this is not a duplicate.

[DomClark]

What is the justification for doing this? We use weak JACK to avoid a hard runtime dependency on JACK, which must be installed separately and cannot be shipped with LMMS. To quote the Weak-JACK readme:

The jack shared library needs to be installed system-wide (for all jack applications to share), it can not be part of an application itself.
[...]
weak-jack linking is useful (at least) in the following cases:

• the resulting application should not be directly linked to libjack.[so|dll|dylib] IOW: the application should start even if libjack is not installed.