[css-ui] Resolve Issue 26 add 'cursor' values 'grab' and 'grabbing' per existing interop in Gecko and -webkit- prefixed in Webkit

Author: tantek

css-ui/Overview.bs

@@ -1257,7 +1257,7 @@ then only the end ellipsis/string should be rendered.
 [ auto | default | none |<br>
  context-menu | help | pointer | progress | wait | <br>
  cell | crosshair | text | vertical-text | <br>
- alias | copy | move | no-drop | not-allowed | <br>
+ alias | copy | move | no-drop | not-allowed | grab | grabbing | <br>
  e-resize | n-resize | ne-resize | nw-resize | s-resize | se-resize | sw-resize | w-resize |
  ew-resize | ns-resize | nesw-resize | nwse-resize |
  col-resize | row-resize |
@@ -1380,6 +1380,10 @@ Often rendered as a hand or pointer with a small circle with a line through it.
 <dd>Indicates that the requested action will not be carried out.
 Often rendered as a circle with a line through it.
 </dd>
+<dt style="cursor:grab">grab</dt>
+<dd>Indicates that something can be grabbed (dragged to be moved). Often rendered as the backside of an open hand.</dd>
+<dt style="cursor:grabbing">grabbing</dt>
+<dd>Indicates that something is being grabbed (dragged to be moved). Often rendered as the backside of a hand with fingers closed mostly out of view.</dd>
 </dl>
 
 resizing and scrolling cursors