Added preparation for GPU hardware accelerated solvers for BulletSoftBody (OpenCL and DirectCompute backends will follow)

Added assert to check for positive masses in btCompoundShape::calculatePrincipalAxisTransform, see Issue 399
Fixes for LLVM/GCC compilation issue in btSequentialImpulseConstraintSolver
(Untested) fix for Linux 64bit compilation Issue 409

src/BulletSoftBody/btSoftRigidDynamicsWorld.h

@@ -21,6 +21,8 @@ subject to the following restrictions:
 
 typedef	btAlignedObjectArray<btSoftBody*> btSoftBodyArray;
 
+class btSoftBodySolver;
+
 class btSoftRigidDynamicsWorld : public btDiscreteDynamicsWorld
 {
 
@@ -30,6 +32,9 @@ class btSoftRigidDynamicsWorld : public btDiscreteDynamicsWorld
 	bool			m_drawFaceTree;
 	bool			m_drawClusterTree;
 	btSoftBodyWorldInfo m_sbi;
+	///Solver classes that encapsulate multiple soft bodies for solving
+	btSoftBodySolver *m_softBodySolver;
+	bool			m_ownsSolver;
 
 protected:
 
@@ -37,14 +42,12 @@ protected:
 
 	virtual void	internalSingleStepSimulation( btScalar timeStep);
 
-	void	updateSoftBodies();
-
-	void	solveSoftBodiesConstraints();
+	void	solveSoftBodiesConstraints( btScalar timeStep );
 
 
 public:
 
-	btSoftRigidDynamicsWorld(btDispatcher* dispatcher,btBroadphaseInterface* pairCache,btConstraintSolver* constraintSolver,btCollisionConfiguration* collisionConfiguration);
+	btSoftRigidDynamicsWorld(btDispatcher* dispatcher,btBroadphaseInterface* pairCache,btConstraintSolver* constraintSolver, btCollisionConfiguration* collisionConfiguration, btSoftBodySolver *softBodySolver = 0 );
 
 	virtual ~btSoftRigidDynamicsWorld();
 
@@ -92,6 +95,7 @@ public:
 					  const btTransform& colObjWorldTransform,
 					  RayResultCallback& resultCallback);
 
+
 };
 
 #endif //BT_SOFT_RIGID_DYNAMICS_WORLD_H