Fix 'hang up' icon size in menu, remove extra menuitem2

At the same time, i also changed the stock ID from 'stop' to 'cancel' since
cancel was actually used for the toolbar 'hang up' button.  In my current theme,
the stop and cancel buttons are the same, but in theory they could be different,
so it's safer to use the same stock ID.
This fixes bug #570397

From: Jonathon Jongsma <jonathon.jongsma@collabora.co.uk>
Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
svn path=/trunk/; revision=2438