replace (:) with 0 in meta-predicate declarations, remove support for (:) in meta-predicate declarations

src/machine/loader.rs

@@ -1498,8 +1498,6 @@ impl Machine {
 
         match self.indices.get_meta_predicate_spec(predicate_name, arity, &compilation_target) {
             Some(meta_specs) => {
-                let op_spec = fetch_op_spec(clause_name!(":"), 2, &self.indices.op_dir);
-
                 let list_loc = self.machine_st.heap.to_list(
                     meta_specs.iter().map(|meta_spec| {
                         match meta_spec {
@@ -1509,9 +1507,6 @@ impl Machine {
                             MetaSpec::RequiresExpansionWithArgument(ref arg_num) => {
                                 HeapCellValue::Addr(Addr::Usize(*arg_num))
                             }
-                            MetaSpec::RequiresExpansion => {
-                                HeapCellValue::Atom(clause_name!(":"), op_spec.clone())
-                            }
                         }
                     }),
                 );

src/machine/preprocessor.rs

@@ -347,7 +347,6 @@ fn setup_meta_predicate<'a>(
                 Term::Constant(_, Constant::Atom(meta_spec, _)) => {
                     let meta_spec =
                         match meta_spec.as_str() {
-                            ":" => MetaSpec::RequiresExpansion,
                             "+" => MetaSpec::Plus,
                             "-" => MetaSpec::Minus,
                             "?" => MetaSpec::Either,