rename convert to op_convert_list and APIfy
fix type incompatibilities between format strings/args

Building a debugging perl triggered warnings such as

warning: format ‘%d’ expects argument of type ‘int’, but argument 3 has type ‘U32’
warning: field width specifier ‘*’ expects argument of type ‘int’, but argument 5 has type ‘long unsigned int’
warning: format ‘%x’ expects argument of type ‘unsigned int’, but argument 3 has type ‘wchar_t’