incompatible changes:
- classfile: support multiple work-classes (#1380)
- classfile: register => import (#1404)
- classfile: rename .gopx => .gox (#1403)
- classfile: IsClass => ClassKind (#1404)
new features:
- classfile: support embed type (starExpr/selectorExpr) (#1386)
- classfile: field var support tag (#1393)
- classfile: support main.spx (#1404)
- compiler check untyped overflows for int128/uint128 (#1384)
changes: