Fix of instance rotations from the side panel

in regard to instance synchronization.

src/slic3r/GUI/GLCanvas3D.cpp

@@ -1271,6 +1271,7 @@ void GLCanvas3D::Selection::rotate(const Vec3d& rotation, GLCanvas3D::Transforma
     assert(! transformation_type.world() || transformation_type.relative());
 
     int rot_axis_max;
+    //FIXME this does not work for absolute rotations (transformation_type.absolute() is true)
     rotation.cwiseAbs().maxCoeff(&rot_axis_max);
 
 	// For generic rotation, we want to rotate the first volume in selection, and then to synchronize the other volumes with it.

src/slic3r/GUI/GUI_ObjectManipulation.cpp

@@ -365,7 +365,8 @@ void ObjectManipulation::change_rotation_value(const Vec3d& rotation)
 	if (selection.is_single_full_instance() || selection.requires_local_axes())
 		transformation_type.set_independent();
 	if (selection.is_single_full_instance()) {
-		transformation_type.set_absolute();
+        //FIXME GLCanvas3D::Selection::rotate() does not process absoulte rotations correctly: It does not recognize the axis index, which was changed.
+		// transformation_type.set_absolute();
 		transformation_type.set_local();
 	}