On iTerm2 on OS X, the Option+Arrow keys produce special sequences
that start with two escapes.  Catch these sequences and interpret
them appropriately as WordLeft / WordRight / Home / End.
Signed-off-by: Mike Scalora <mike@scalora.org>
Signed-off-by: Thomas Rosenau <thomasr@fantasymail.de>
Signed-off-by: Benno Schulenberg <bensberg@justemail.net>