Nasty feature in new cursor...

[Tuomas Lukka <lukka@xxxxxxxxxxx>]

One slightly nasty feature in the three-dimension cursor stuff is that
making cursor move atomic is suddenly much harder. Previously, that was
one insert away, but now moving a cursor DISCONNECTS ALL OTHER CURSORS FOR
A MOMENT. 

This may not seem like a big deal but once you realize that headcell is
used for observation then it will be seen that moving a cursor can then
trigger a lot of events.

Hmm... I don't like this.

	Tuomas