Added SmokeTrailEffect which renders created particles as single quad or line

strip, in the case of the quad strip the strip is aligned to the be orthogonal with
the eye point.

include/osgParticle/ParticleSystem

@@ -123,6 +123,9 @@ namespace osgParticle
         /// Destroy the i-th particle.
         inline virtual void destroyParticle(int i);
         
+        /// Reuse the i-th particle.
+        inline virtual void reuseParticle(int i) { _deadparts.push(&(_particles[i])); }
+
         /// Get the last frame number.
         inline int getLastFrameNumber() const;
 
@@ -170,7 +173,6 @@ namespace osgParticle
         inline void update_bounds(const osg::Vec3& p, float r);
         void single_pass_render(osg::State& state, const osg::Matrix& modelview) const;
 
-    private:
         typedef std::vector<Particle> Particle_vector;
         typedef std::stack<Particle*> Death_stack;