This is only a small refactoring step towards a editor-free
CppEditorSupport.

Left are m_editor references that need to be addressed.

No functional change.

Change-Id: I9fc7b0abfe88f5b9a6ce3f57a5c4a922ae953ddf
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>