[*] Updated declarations for LTK-2.3
[LTK-Editor] Added support to restart content assist session and util for
lazy loading

Signed-off-by: Stephan Wahlbrink <sw@wahlbrink.eu>
[LTK-Editor] Added additional command handlers for source editors allowing
to replace text widget operations (ST)
  - Added 'Go to line start/end', supporting smart begin/end
  - Added 'Select to line start/end', supporting smart begin/end

Signed-off-by: Stephan Wahlbrink <sw@wahlbrink.eu>