libedit: Upgrade NetBSD version 2011-03-11

libedit: Upgrade NetBSD version 2011-03-11

As NetBSD has properly packaged regular releases of their libedit
library (readline replacement), a new vendor branch has been created
for it.  Libedit was last synchronized with NetBSD 4 years ago, to
the week.

During that time, a new function was added to the DragonFly version
that still doesn't exist on NetBSD.  It is necessary to support GDB
7.x, so the addition of rl_completion_word_break_hook function has
been carried over to this update.