Obj tag method.
Obj is_val.
is_ref, is_ptr, is_int, is_sym.
is_bool, is_data_word.
is_data_ref, is_data, is_env, is_cmpd, is_type.
Obj type, id_hash, counter_index.
remove dynamic format checking.
_exc_raise no longer variadic.
fmt_to_file now uses variadic templates.