a dox summary header for the mobility support

SConstruct

@@ -268,6 +268,9 @@ mobility.add_inst_headers ([
     'random-topology.h',
     'ns2-mobility-file-topology.h',
     ])
+mobility.add_headers ([
+    'mobility.h'
+    ])
 
 node = build.Ns3Module ('node', 'src/node')
 ns3.add (node)

src/mobility/mobility.h

@@ -0,0 +1,42 @@
+/**
+ * \defgroup mobility Mobility
+ *
+ * The mobility support includes:
+ *  - a set of mobility models which are used to track and maintain
+ *    the "current" cartesian position and speed of an object.
+ *
+ *  - a "course change notifier" which can be used to register listeners
+ *    to the course changes of a mobility model: ns3::MobilityModelNotifier.
+ *
+ *  - a set of topology constructors which are used to set the initial
+ *    position and associate a specific mobility model to a set of objects.
+ *
+ * The mobility models themselves are:
+ *   - StaticMobilityModel: a model which maintains a constant position
+ *     until it is changed by the user.
+ *
+ *   - StaticSpeedMobilityModel: a model which maintains a constant speed
+ *     until it is changed by the user.
+ *
+ *   - HierarchicalMobilityModel: a model which calculates the current 
+ *     absolute position from a "reference" (parent) mobility model
+ *     and a "relative" (child) mobility model. This allows users to
+ *     compose mobility models.
+ *
+ *   - RandomWalk2dMobilityModel: a 2d "brownian" motion mobility model
+ *     where the bounds of the mobility area are a rectangle.
+ *
+ *   - RandomWaypointMobilityModel: a 3d random waypoint mobility model.
+ *
+ *   - RandomDirection2dMobilityModel: a 2d random direction mobility
+ *     model where the bounds of the mobility are are a rectangle.
+ *
+ * The topology constructors:
+ *   - GridTopology: layout objects in a 2d grid.
+ *
+ *   - RandomTopology: layout objects in a 3d space, according to a 
+ *     RandomPosition model.
+ *
+ *   - Ns2MobilityFileTopology: layout objects in a 3d space according
+ *     to an ns2 CMU mobility file (as generated by the setdest tool).
+ */