added gyroscopic force option for btRigidBody, body->setFlags(BT_ENABLE_GYROPSCOPIC_FORCE);

Note that it can easily introduce instability at regular (60Hertz) simulation steps so it is generally best to not use the option.
If needed, use a very small internal step, such as 1000 Hertz (world->stepSimulation(dt,100,1./1000.f); or stepSimulation(1./1000.,0);

Demos/GyroscopicDemo/main.cpp

@@ -0,0 +1,20 @@
+#include "GyroscopicDemo.h"
+#include "GlutStuff.h"
+#include "GLDebugDrawer.h"
+
+#include "btBulletDynamicsCommon.h"
+
+int main(int argc,char** argv)
+{
+
+	
+
+    GyroscopicDemo* constraintDemo = new GyroscopicDemo();
+	
+
+    constraintDemo->initPhysics();
+	constraintDemo->setDebugMode(btIDebugDraw::DBG_DrawConstraints+btIDebugDraw::DBG_DrawConstraintLimits);
+	
+	return glutmain(argc, argv,640,480,"Constraint Demo. http://www.continuousphysics.com/Bullet/phpBB2/",constraintDemo);
+}
+