Using the safe unicode representation of the minus sign.

No functional change; see openlayers#588.

Author: ahocevar

lib/OpenLayers/Control/Zoom.js

@@ -37,9 +37,9 @@ OpenLayers.Control.Zoom = OpenLayers.Class(OpenLayers.Control, {
     /**
      * APIProperty: zoomOutText
      * {String}
-     * Text for zoom-out link.  Default is "−".
+     * Text for zoom-out link.  Default is "\u2212".
      */
-    zoomOutText: "−",
+    zoomOutText: "\u2212",
 
     /**
      * APIProperty: zoomOutId