Adds "Efl.Ui.Text_Async" object.
This new widget uses the "async_layout" functionality of the underlying
Efl.Canvas.Text object.
Currently, if "editable" mode is enabled, there is no asynchronous
layout, as interactive operations (e.g. typing) should get processed
immediately. Thus, only "non-editable" instructs the text object to do
asynchronous layout.
@feature
Daniel Hirt