// types list (see predeclared in bexport.go for order). Otherwise,
// subtracting predeclReserved yields the offset of a type descriptor.
//
// Value means a type, kind, and type-specific value. See
// (*exportWriter).value for details.
//
//
// There are twelve kinds of type descriptors, distinguished by an itag:
//
//     type DefinedType struct {
//         Tag     itag // definedType
//         Name    stringOff