Braille patterns should also be usable in Compose.  This combines the
implementation of braille chords and compose tree: only emit the braille
pattern if it can not be found in the compose tree, if any.
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Backported-to-NX-by: Ulrich Sibiller <uli42@gmx.de>