Ensure resizing editor sidebar works over iframes
Ensure resizing editor sidebar works over iframes

The option prevents iframes from capturing mouse events, which can
cause the dragged resizer to get stuck. This used to be a problem
already with rich text editors, which are iframes. Now that the
preview uses an iframe the problem got worse.

REDMINE-17258

tf/pageflow,tf/pageflow,codevise/pageflow,codevise/pageflow,tf/pageflow,codevise/pageflow,tf/pageflow,codevise/pageflow