Fix inexplicable 5.8.x C3 errors - roll back e6efde04

Fix inexplicable 5.8.x C3 errors - roll back e6efde04

The optimization ends up breaking the entire C3 subsystem at a crucial time
when add_columns has to see the correct register_column in order for IC::DT
to populate the right column_info.

Most importantly it seems that Class::C3::XS makes this optimization entirely
moot (in fact minimal testing indicates things getting *faster* instead)