editeng tiled rendering: implement drag of start/end selection handle
editeng tiled rendering: implement drag of start/end selection handle

With this, it's possible to drag the handle of not only the normal
cursor, but also the start/end handle of a range selection in editeng
text, e.g. Writer shape text.

Change-Id: I5b9f548fb6365ecb499c68cef0d89f7f8ff3a11d

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core