add a map getUnits method, r=ahocevar (Closes 1591)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@7374 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Control/OverviewMap.js

@@ -495,7 +495,7 @@ OpenLayers.Control.OverviewMap = OpenLayers.Class(OpenLayers.Control, {
     updateRectToMap: function() {
         // The base layer for overview map needs to be in the same projection
         // as the base layer for the main map.  This should be made more robust.
-        if(this.map.units != 'degrees') {
+        if(this.map.getUnits() != 'degrees') {
             if(this.ovmap.getProjection() && (this.map.getProjection() != this.ovmap.getProjection())) {
                 alert(OpenLayers.i18n("sameProjection"));
             }

lib/OpenLayers/Control/ScaleLine.js

@@ -153,7 +153,7 @@ OpenLayers.Control.ScaleLine = OpenLayers.Class(OpenLayers.Control, {
             return;
         }
 
-        var curMapUnits = this.map.units;
+        var curMapUnits = this.map.getUnits();
         var inches = OpenLayers.INCHES_PER_UNIT;
 
         // convert maxWidth to map units

lib/OpenLayers/Map.js

@@ -1763,6 +1763,21 @@ OpenLayers.Map = OpenLayers.Class({
         return resolution;
     },
 
+    /**
+     * APIMethod: getUnits
+     * 
+     * Returns:
+     * {Float} The current units of the map. 
+     *         If no baselayer is set, returns null.
+     */
+    getUnits: function () {
+        var units = null;
+        if (this.baseLayer != null) {
+            units = this.baseLayer.units;
+        }
+        return units;
+    },
+
      /**
       * APIMethod: getScale
       *