update version number to rc7

Author: Bart van den Eijnden

lib/OpenLayers.js

@@ -426,4 +426,4 @@
  * When asking questions or reporting issues, make sure to include the output of
  *     OpenLayers.VERSION_NUMBER in the question or issue-description.
  */
-OpenLayers.VERSION_NUMBER="Release 2.13-rc6";
+OpenLayers.VERSION_NUMBER="Release 2.13-rc7";

lib/OpenLayers/SingleFile.js

@@ -7,7 +7,7 @@ var OpenLayers = {
     /**
      * Constant: VERSION_NUMBER
      */
-    VERSION_NUMBER: "Release 2.13-rc6",
+    VERSION_NUMBER: "Release 2.13-rc7",
 
     /**
      * Constant: singleFile