Disable antialiasing while dragging

[g-rden]

While the left mouse button is pressed down antialiasing is now disabled.

Reason: Dragging while antialiasing is enabled is unusable on some machines.

[artemsen]

This is a very extraordinary solution, but its implementation looks like a hack, especially "let's redraw on every mouse key event" =)
The main complaint is that the entire solution is based on the fact that ui_redraw() is a synchronous operation. This works now, but I plan to change the logic to event-driven model and ui_redraw will be called asynchronously.
So, even if we merge this PR, this solution will not survive to release.

[g-rden]

very extraordinary solution

lol, yeah I am no programmer.

"let's redraw on every mouse key event"

That is not happening. It only gets drawn when the mouse button is first pressed down and then when it is released again.

this solution will not survive to release.

Fair.