Fix raw32 terrain heightmap reader so it estimates terrain size from

the size of the input stream. This is required since the raw heightmap
format (.r32) does not contain any size information.
The estimation relies on terrain being square.

OpenSim/Region/Framework/Scenes/TerrainChannel.cs

@@ -217,6 +217,10 @@ namespace OpenSim.Region.Framework.Scenes
         // ITerrainChannel.Merge
         public void Merge(ITerrainChannel newTerrain, Vector3 displacement, float radianRotation, Vector2 rotationDisplacement)
         {
+            m_log.DebugFormat("{0} Merge. inSize=<{1},{2}>, disp={3}, rot={4}, rotDisp={5}, outSize=<{6},{7}>", LogHeader,
+                                        newTerrain.Width, newTerrain.Height,
+                                        displacement, radianRotation, rotationDisplacement,
+                                        m_terrainData.SizeX, m_terrainData.SizeY);
             for (int xx = 0; xx < newTerrain.Width; xx++)
             {
                 for (int yy = 0; yy < newTerrain.Height; yy++)