fix Collada: wrong usage of pointer and hidden redeclaration

* Suspicious usage of pointer:

  short *type = 0; // this creates a null pointer

When this is later used for anything then blender would crash.
After following the code and check what happens i strongly believe
the author wanted to use a short and not a pointer to a short here.

* local variable where reused later in same function
While this did no harm, i still felt it was better to use a different
name here to make things more separated:

- moved variable declaraiotns into loop (for int a=0; ...)
- renamed uv_images to uv_image_set
- renamed index variable from i to j in inner loop that
  reused same index name from outer loop

source/blender/collada/DocumentImporter.cpp

@@ -474,9 +474,9 @@ void DocumentImporter::create_constraints(ExtraTags *et, Object *ob)
 {
 	if (et && et->isProfile("blender")) {
 		std::string name;
-		short* type = 0;
-		et->setData("type", type);
-		BKE_constraint_add_for_object(ob, "Test_con", *type);
+		short type = 0;
+		et->setData("type", &type);
+		BKE_constraint_add_for_object(ob, "Test_con", type);
 		
 	}
 }
@@ -587,8 +587,8 @@ std::vector<Object *> *DocumentImporter::write_node(COLLADAFW::Node *node, COLLA
 			++lamp_done;
 		}
 		while (controller_done < controller.getCount()) {
-			COLLADAFW::InstanceGeometry *geom = (COLLADAFW::InstanceGeometry *)controller[controller_done];
-			ob = mesh_importer.create_mesh_object(node, geom, true, uid_material_map, material_texture_mapping_map);
+			COLLADAFW::InstanceGeometry *geometry = (COLLADAFW::InstanceGeometry *)controller[controller_done];
+			ob = mesh_importer.create_mesh_object(node, geometry, true, uid_material_map, material_texture_mapping_map);
 			if (ob == NULL) {
 				report_unknown_reference(*node, "instance_controller");
 			}