Instead of right click, the skeleton key is now a true `tool`
in the sense that it's default left-click action is to create
a key for the locked object.
This is far better than the outcome of the patches we've done
where the only way to create a key for a locked item was to
use sneak+rightclick. Now keys are perhaps a bit more sensible,
left for making keys, right for opening stuff with keys.
Fixes #1625
61d7c43c83