News in 3.21.3
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* Warn when a secondary public header is #included in external code.
  Only <gtksourceview/gtksource.h> should be #included directly.
* Remove the --disable-completion-providers configure option, to always build
  the completion providers. There is currently only one completion provider:
  GtkSourceCompletionWords, which is not a lot of code and doesn't pull up
  additional dependencies.
* Add back the gtksourceview-typebuiltins.h public header, for backward
  compatibility.
* Fixes/improvements to the Visual Studio builds
* Improvements to the syntax highlighting of: rpmspec
* Fix a bug in GtkSourceSearchContext
* Various small code and documentation improvements
* Translation updates