Expose getPointedThing to Lua

This commit introduces Raycast, a Lua user object, which can be
used to perform a raycast on the map. The ray is continuable, so one can
also get hidden nodes (for example to see trough glass).

src/environment.h

@@ -42,6 +42,8 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 class IGameDef;
 class Map;
+struct PointedThing;
+class RaycastState;
 
 class Environment
 {
@@ -76,6 +78,26 @@ public:
 
 	u32 getDayCount();
 
+	/*!
+	 * Gets the objects pointed by the shootline as
+	 * pointed things.
+	 * If this is a client environment, the local player
+	 * won't be returned.
+	 * @param[in]  shootline_on_map the shootline for
+	 * the test in world coordinates
+	 *
+	 * @param[out] objects          found objects
+	 */
+	virtual void getSelectedActiveObjects(const core::line3d<f32> &shootline_on_map,
+			std::vector<PointedThing> &objects) = 0;
+
+	/*!
+	 * Returns the next node or object the shootline meets.
+	 * @param state current state of the raycast
+	 * @result output, will contain the next pointed thing
+	 */
+	void continueRaycast(RaycastState *state, PointedThing *result);
+
 	// counter used internally when triggering ABMs
 	u32 m_added_objects;