SGPropertyNode: add InterpolationMgr getter.

simgear/props/props.cxx

@@ -1695,6 +1695,12 @@ void SGPropertyNode::setInterpolationMgr(simgear::PropertyInterpolationMgr* mgr)
   _interpolation_mgr = mgr;
 }
 
+//------------------------------------------------------------------------------
+simgear::PropertyInterpolationMgr* SGPropertyNode::getInterpolationMgr()
+{
+  return _interpolation_mgr;
+}
+
 simgear::PropertyInterpolationMgr* SGPropertyNode::_interpolation_mgr = 0;
 
 //------------------------------------------------------------------------------

simgear/props/props.hxx

@@ -1302,6 +1302,11 @@ public:
    */
   static void setInterpolationMgr(simgear::PropertyInterpolationMgr* mgr);
 
+  /**
+   * Get the interpolation manager
+   */
+  static simgear::PropertyInterpolationMgr* getInterpolationMgr();
+
   /**
    * Print the value of the property to a stream.
    */