Make val_id and var_syms CORE funs
Make val_id and var_syms CORE funs, so that a new val only contains .repr method
CORE.id must be renamed as CORE.identity
Working on issue_0043293-move-val_id-var_syms
Closed by 91f211a4efdbdc133088d5401fee1c60db6d698a
Make val_id and var_syms CORE funs, so that a new val only contains .repr method