a) split the textengine selection changed broadcast into a text selection changed
and text caret change event
b) handle both in existing places that handled the text selection event
c) listen for them in VclMultiLineEdit and translate to
VCLEVENT_EDIT_SELECTIONCHANGED VCLEVENT_EDIT_CARETCHANGED events
d) profit from the VCLEVENT_EDIT_SELECTIONCHANGED and
VCLEVENT_EDIT_CARETCHANGED handling in
accessibility/source/standard/vclxaccessibleedit.cxx for VCLXAccessibleEdits

Change-Id: I09187e76ae4eb189ee9469e388374154087faf80