Log Message:
Import gtksourcecompletion-0.5.2 as wip/gtksourcecompletion.

GtkSourceCompletion is a library to add (auto)completion
and calltips support to GtkSourceView. The library manages all events,
etc  the popup position but it doesn't complete anything,
it is the base library. You can develop providers for GtkSourceCompletion and
the library will use it to show all the proposals,
the information for every proposal etc