fix memory issues in btSparseSDF.h

(hash function on structure with uninitialized padding, and  Reset not called in destructor)
expose sparseSdfVoxelSize in PyBullet.setPhysicsEngineParameter
don't call deformable wireframe drawing in the wrong thread/place (it can cause crashes)

src/BulletSoftBody/btDeformableMultiBodyDynamicsWorld.cpp

@@ -382,6 +382,8 @@ void btDeformableMultiBodyDynamicsWorld::reinitialize(btScalar timeStep)
 void btDeformableMultiBodyDynamicsWorld::debugDrawWorld()
 {
 
+	btMultiBodyDynamicsWorld::debugDrawWorld();
+
 	for (int i = 0; i < getSoftBodyArray().size(); i++)
 	{
 		btSoftBody* psb = (btSoftBody*)getSoftBodyArray()[i];
@@ -391,7 +393,7 @@ void btDeformableMultiBodyDynamicsWorld::debugDrawWorld()
 		}
 	}
 
-	btMultiBodyDynamicsWorld::debugDrawWorld();
+	
 }
 
 void btDeformableMultiBodyDynamicsWorld::applyRigidBodyGravity(btScalar timeStep)

src/BulletSoftBody/btSparseSDF.h

@@ -77,6 +77,10 @@ struct btSparseSdf
 	int nprobes;
 	int nqueries;
 
+	~btSparseSdf()
+	{
+		Reset();
+	}
 	//
 	// Methods
 	//
@@ -330,15 +334,18 @@ struct btSparseSdf
 	{
 		struct btS
 		{
-			int x, y, z;
+			int x, y, z, w;
 			void* p;
 		};
 
 		btS myset;
+		//memset may be needed in case of additional (uninitialized) padding!
+		//memset(myset, 0, sizeof(btS));
 
 		myset.x = x;
 		myset.y = y;
 		myset.z = z;
+		myset.w = 0;
 		myset.p = (void*)shape;
 		const void* ptr = &myset;