Hi Campbell,
this patch implement CTRL+LEFTMOUSE as a way to cut the linking between Logic Bricks. "Copied" from the Node system.

However Matt suggests that it shouldn't be an operator but handled in the interface_handlers. I will have no time to work on that before Feb 1st, so if you can take a look at that it would be great.

Thanks,
Dalai
(there are some hacks in this solution. but they would go away if the implementation were in interface)