Fix library name in features-available.
Fix automake --gnu warnings.

Fixes #4755
Add tools/.gitignore.
Fix the m4 include path.

Fixes #4415
configure: Show whether MySQL/Python support is enabled

Fixes #4763
Update requirements list in the INSTALL file.

Fixes #4745
Update .gitignore file.
Fix Notification::user_groups validator (rename from Notification::groups).

Fixes #4753