add a MultiMap Layer Removal section in the 2.12 release notes

Author: elemoine

notes/2.12.md

@@ -138,6 +138,14 @@ Corresponding issues/pull requests:
 
 # Behavior Changes from Past Releases
 
+## MultiMap Layer Removal
+
+The `OpenLayers.Layer.MultiMap` class has been removed entirely, as the MultiMap service was discontinued.
+
+Corresponding issues/pull requests:
+
+ * https://github.com/openlayers/openlayers/pull/328
+
 ## GPX API change
 
 The `gpxns` API property has been removed. The GPX namespace is now defined in the `namespaces` property but is not intended to be overriden.
@@ -321,7 +329,6 @@ A number of properties, methods, and constructors have been marked as deprecated
  * OpenLayers.Tile.WFS
  * OpenLayers.Feature.WFS
  * OpenLayers.Layer.WFS
- * OpenLayers.Layer.MultiMap
  * OpenLayers.Layer.VirtualEarth
  * OpenLayers.Protocol.SQL
  * OpenLayers.Protocol.SQL.Gears