When we move from one surface to another we ought to handle leave for the old one but also send enter for the new one.
The disable signal on text-input objects must not be ignored. It is only sent when the previous state was enabled.
The compositor acts as a relay between applications using the text-input protocol and input methods using the input-method protocol. This change implements the basic but useful support for input-method, leaving out grabs as well as popups.
