DnD icons don't work in IE

Hi there,

Unfortunately the DnD icons don't display in IE, specifically the green arrow (for valid drop target) and the red 'ban' icon (for invalid drop target). I'm testing in IE11, but also tried IE9 (using the emulation tab) and neither works. Chrome and Firefox (latest versions) are happy.

To reproduce, perform DnD on the test page: http://yiweima.github.io/flatdojo/pages/others.html#dnd

I did have some luck getting the icons to display in IE by adding the following CSS rule to my HTML body:

html, body {
...
font-family: Arial, Helvetica, sans-serif, **FontAwesome**; /\* <= Added _FontAwesome_ here */
...
}

This allowed the arrow/ban icons to show, but only in black which isn't ideal. The css file I tinkered with is /dojo/Common.css, specifically the 4x styles that set content to "\f05e" and "\f060".

Cheers,
Jan