divider bars do not animate when moved

[daxim]

1. Grab a window divider bar with the mouse, e.g. the divider between the main document area and the three lower panes.
2. Move it up.

What should happen:
Lower pane area grows and document area shrinks in a smooth animation, like in Kate, Gedit, Opera, Firefox.

What really happens:
Under the mouse cursor appears a dotted line. Dragging the mouse moves the dotted line. The divider bar stays where it is. Areas do not change their size. When the mouse button is let go, the position of the dotted line becomes the new position of the divider bar. Areas are updated instantaneously.

[daxim]

Not fixed as of r18904.