dismiss all popups on mouse drags, e.g. to avoid conflict of C-hover of Isabelle/jEdit and C-selection of jEdit;

--- a/src/Tools/jEdit/src/rich_text_area.scala	Sat Mar 29 12:05:24 2014 +0100
+++ b/src/Tools/jEdit/src/rich_text_area.scala	Sat Mar 29 12:42:24 2014 +0100
@@ -181,6 +181,12 @@
   }
 
   private val mouse_motion_listener = new MouseMotionAdapter {
+    override def mouseDragged(evt: MouseEvent) {
+      robust_body(()) {
+        PIDE.dismissed_popups(view)
+      }
+    }
+
     override def mouseMoved(evt: MouseEvent) {
       robust_body(()) {
         val x = evt.getX