add basic debug drawing interface for btMultiBodyPoint2Point constraint

add basic debug drawing drawText3D in SimpleOpenGL3App
remove a few warnings
add drawTexturedRect3D to GLPrimitiveRenderer to support debug drawing

Demos3/bullet2/BasicConcepts/CoordinateSystemDemo.h

@@ -60,6 +60,9 @@ public:
     virtual void	renderScene()
     {
 		m_app->m_renderer->renderScene();
+		m_app->drawText3D("X",1,0,0,1);
+		m_app->drawText3D("Y",0,1,0,1);
+		m_app->drawText3D("Z",0,0,1,1);
     }
 
 	virtual void drawArc(const btVector3& center, const btVector3& normal, const btVector3& axis, btScalar radiusA, btScalar radiusB, btScalar minAngle, btScalar maxAngle, 

Demos3/bullet2/CoordinateFrameDemo/CoordinateFrameDemoPhysicsSetup.cpp

@@ -21,6 +21,7 @@ void    CoordinateFrameDemoPhysicsSetup::debugDraw()
 		}
 	}
 	*/
+
 	m_dynamicsWorld->debugDrawWorld();
 }