Prepare for 2.6.1
Group construct updates by Y for efficiency

This probably won't have an effect unless I implement batch updates.
Batch construction updates.

This lets you build huge things without killing the server. Need to
apply similar logic to fill and maybe recurse.
Temporarily (?) change shrink's icon again.
Add a feature to this I won't end up using.
Batch up fill changes.
Fix contstruction radius
Change alter icon- this one has problems too.
Change the default fill limits.
Fix wands that consume XP