Configure mods menu: scrolling by clicking arrows or bar enables/disables mods

[paramat]

Bug is present in recent commit 4ca and in 0.4.10 stable.
Also, scrolling by click-and-hold on arrows does not work.

[kahrl]

This happens with other tables too (e.g. serverlist, credits). I'll investigate this.

[kahrl]

The first bug was introduced by 8966c16.
The second bug has always been present because that's how Irrlicht scrollbars work.

[codyharrington]

This seems to be double-click related. For me, if you click the scroll arrow with enough pause in between clicks, it doesn't happen. But if you click fast, i.e. what would be registered as a double click, it selects the item on the mouseDown event. I'm currently looking into it myself.