Without this patch, the text area would mistakenly delete the characters
types after placing the cursor with the mouse as soon as shift is used
as modifier.
The new text_area component is able to view and edit files.
Internally, it employs a menu_view for the graphics output.
Only basic notepad-like text-editing functions are supported.
At the current time, it is solely meant as a companion of the Sculpt
manager.
Issue #3650
