Annex implementations cannot use new Xtext (>= 2.9) workflows

[lwrage]

The new Xtext workflow generate a performance optimized parser for content assist functionality. Using content assist in such an annex breaks all functionality of the text editor such that it must be closed and re-opened. The old content assist parser works fine.
Need to investigate if/how annex aware content assist can be made to work with the new style partial content assist parser.