Allow default function/hook/event parameters. Addresses #972.

And changed the endianness parameter of bytestring_to_count() BIF to
default to false (big endian), mostly just to prove that the BIF parser
doesn't choke on default parameters.

src/Expr.cc

@@ -5478,6 +5478,50 @@ int check_and_promote_exprs(ListExpr*& elements, TypeList* types)
 	return 1;
 	}
 
+int check_and_promote_args(ListExpr*& args, RecordType* types)
+	{
+	expr_list& el = args->Exprs();
+	int ntypes = types->NumFields();
+
+	// give variadic BIFs automatic pass
+	if ( ntypes == 1 && types->FieldDecl(0)->type->Tag() == TYPE_ANY )
+		return 1;
+
+	if ( el.length() < ntypes )
+		{
+		expr_list def_elements;
+
+		// Start from rightmost parameter, work backward to fill in missing
+		// arguments using &default expressions.
+		for ( int i = ntypes - 1; i >= el.length(); --i )
+			{
+			TypeDecl* td = types->FieldDecl(i);
+			Attr* def_attr = td->attrs ? td->attrs->FindAttr(ATTR_DEFAULT) : 0;
+
+			if ( ! def_attr )
+				{
+				types->Error("parameter mismatch", args);
+				return 0;
+				}
+
+			def_elements.insert(def_attr->AttrExpr());
+			}
+
+		loop_over_list(def_elements, i)
+			el.append(def_elements[i]->Ref());
+		}
+
+	TypeList* tl = new TypeList();
+
+	for ( int i = 0; i < types->NumFields(); ++i )
+		tl->Append(types->FieldType(i)->Ref());
+
+	int rval = check_and_promote_exprs(args, tl);
+	Unref(tl);
+
+	return rval;
+	}
+
 int check_and_promote_exprs_to_type(ListExpr*& elements, BroType* type)
 	{
 	expr_list& el = elements->Exprs();