Merge some BS1.7 changes:

Boolean operation feature

src/slic3r/GUI/Gizmos/GizmoObjectManipulation.cpp

@@ -452,6 +452,7 @@ void GizmoObjectManipulation::set_uniform_scaling(const bool new_value)
         // all volumes in the selection belongs to the same instance, any of them contains the needed instance data, so we take the first one
         const GLVolume* volume = selection.get_volume(*selection.get_volume_idxs().begin());
         // Is the angle close to a multiple of 90 degrees?
+
 		if (! Geometry::is_rotation_ninety_degrees(volume->get_instance_rotation())) {
             // Cannot apply scaling in the world coordinate system.
             // BBS: remove tilt prompt dialog