Patch to avoid history duplicates applied

[Pavel Roskin <proski gnu org>]

Hello!

I have applied a patch to avoid duplicates in the history.  Unlike the
patch posted on Savannah, it affects both the input widgets and the
directory history.

As a side effect, the lists used for history were converted to GList
(double linked list from glib).

Also, Alt-O writes the directory history now.

-- 
Regards,
Pavel Roskin