TableFun.join/merge: optimize the important special case where the tables coincide -- NOTE: this changes both the operational behaviour and the result for non-standard join/eq notion;

fixed proofs -- follow-up to ecd6f0ca62ea;

renamed NameSpace.base to NameSpace.base_name (in accordance with "full_name"); tuned;

renamed NameSpace.base to NameSpace.base_name; renamed NameSpace.map_base to NameSpace.map_base_name; eliminated alias Sign.base_name = NameSpace.base_name;