Remove old items first in create_toolbar()

Signed-off-by: Jiří Janoušek <janousek.jiri@gmail.com>
Import important vapi from Vala 0.26

The new glib-2.0.vapi also fixes glib >= 2.41.2 and valac < 0.25.2
incompatibility.

http://valajournal.blogspot.cz/2014/12/vala-deadlocks-with-glib-242.html

Signed-off-by: Jiří Janoušek <janousek.jiri@gmail.com>
Revert: glib >= 2.41.2 and valac < 0.25.2 not compatible

Since glib-2.0.vapi from Vala 0.26 has been imported the glib >= 2.41.2
and valac < 0.25.2 incompatibility is fixed.

http://valajournal.blogspot.cz/2014/12/vala-deadlocks-with-glib-242.html

This reverts commit 7829a1036e463b8efd04c65879e8dff5fff6b827.