Allow Undo to affect 3D cursor movement

When working with the 3D cursor, it is a huge hassle when you accidentally click and move it. It would be great if a quick ctrl+z would fix this, but the 3D cursor's movements do not seem to be part of the Undo stack. Doing transforms or snapping with the 3D cursor already requires a lot of button presses, so having this would be very convenient.

As there are situations where you may not like this to happen, it should be an option you can toggle in user preferences.