PreventDefault option for sortables

[ghouston]

I am running into a similar issue as #870, but with sortables. In a horizontal sortable, if there is an anchor tag inside the sortable li item, sortable functionality begins to break down in IE. When you start to drag the item left or right, the cursor turns to a circle with a slash through it. Then when you mouseup IE still thinks you have the mousedown. You have to click somewhere on the page to get the sortable item to fall into place somewhere.

PreventDefault? was added as an option to drag in r1525, but it does not seem to work as an option for sortables. If it is an option for sortables already it is not fixing the issue.