Editor: Handle Tab as printable character.

Task-number: QTCREATORBUG-2225
Change-Id: Ia557e0c1d61b61b31b28a1d3e32f846d7efd70f0
Reviewed-by: Eike Ziller <eike.ziller@digia.com>
CDB: Clarify condition

compare() doesn't return bool, but negative, 0 or positive value.

Change-Id: I9f2becfa0980e0fb738ab27eaa651c45392385db
Reviewed-by: David Schulz <david.schulz@digia.com>