Some fixes to work with constraint angle limits close to -PI or PI

Demos/SliderConstraintDemo/main.cpp

@@ -17,6 +17,7 @@ int main(int argc,char** argv)
 
         sliderConstraintDemo->initPhysics();
 		sliderConstraintDemo->getDynamicsWorld()->setDebugDrawer(&gDebugDrawer);
+		sliderConstraintDemo->setDebugMode(btIDebugDraw::DBG_DrawConstraints+btIDebugDraw::DBG_DrawConstraintLimits);
        
 
         return glutmain(argc, argv,640,480,"Slider Constraint Demo. http://www.continuousphysics.com/Bullet/phpBB2/", sliderConstraintDemo);