more soft body preparations, moved some parts from Demo/SoftBody to src/BulletDynamics/SoftBody

moved Extras/ConvexHull/btConvexHull.* to src/LinearMath/btConvexHull.*
removed btCollisionObject::m_internalOwner, replaced it by m_internalType. This should not affect external API (it was clearly marked as internal)

Demos/SoftDemo/btSoftRigidCollisionAlgorithm.h

@@ -23,7 +23,7 @@ class btPersistentManifold;
 #include "BulletCollision/CollisionDispatch/btCollisionDispatcher.h"
 
 #include "LinearMath/btVector3.h"
-struct  btSoftBody;
+class btSoftBody;
 
 /// btSoftRigidCollisionAlgorithm  provides collision detection between btSoftBody and btRigidBody
 class btSoftRigidCollisionAlgorithm : public btCollisionAlgorithm
@@ -67,3 +67,4 @@ public:
 
 #endif //SOFT_RIGID_COLLISION_ALGORITHM_H
 
+