Added Height Field Fluid Demo to Bullet. All code stored in the Demos/HeightFieldFluidDemo directory for now.

Please see HfFluidDemo.cpp for examples of how to use the height field fluid along with buoyant collision shapes.

The implementation is still lacking in my ways:
1) Need to complete more collision algorithms for buoyant collision shapes
2) Support compound buoyant shapes
3) The buoyancy model isn't that great
4) Fluid volume can be lost over time

Demos/SimplexDemo/SimplexDemo.cpp

@@ -91,7 +91,7 @@ void SimplexDemo::displayCallback()
 		transA.getOpenGLMatrix( m );
 
 		/// draw the simplex
-		m_shapeDrawer.drawOpenGL(m,shapePtr[i],btVector3(1,1,1),getDebugMode(),worldBoundsMin,worldBoundsMax);
+		m_shapeDrawer->drawOpenGL(m,shapePtr[i],btVector3(1,1,1),getDebugMode(),worldBoundsMin,worldBoundsMax);
 
 		/// calculate closest point from simplex to the origin, and draw this vector
 		simplex.calcClosest(m);