atk key: Always convert control character events into key names
including when the control modifier is present, i.e. when one is typing control-I for instance.
Orca would convert them back to the corresponding ASCII letter anyway, and when pressing control-tab, we do want to pass "tab", not pass "\t" that Orca would erroneously convert to "control-I".
Fixes #1743 (closed)
(cherry picked from commit 728f6869)