various 6g cleanup:

various 6g cleanup:

* give genwrapper and genembedtramp the same signature.
* move duint8, duint16, duint32, duint64, duintptr into gc.
* tidy genwrapper.
* bug involving struct field symbols in signature list.
  (hash-order dependent so hard to trigger)
* new Type print format %#-T like %#T but omits
  names on function arguments.

R=ken
OCL=31237
CL=31237