RAW: invalid decoding of octetstring field with LENGTHTO attribute

An octetstring field with the LENGTHTO attribute is not decoded correctly.

type record Rec {
  charstring str1,
  charstring str2,
  octetstring len
}
with {
  encode "RAW";
  variant (str1) "FIELDLENGTH(4)";
  variant (str2) "FIELDLENGTH(3)";
  variant (len) "FIELDLENGTH(2)";
  variant (len) "LENGTHTO(str1, str2)";
  variant (len) "BYTEORDER(first)";
  variant (len) "BITORDER(msb)";
}

control {
  var Rec x := { "abcd", "xyz", 'ABCD'O };
  action(bit2oct(encvalue(x))); // 61626364 78797A E000
  var bitstring y := encvalue(x);
  action(decvalue(y, x));
  action(x); // { str1 := "abcd", str2 := "xyz", len := '00E0'O }
}

In the example field 'len' should be '0007'O after decoding, regardless of other coding attributes.

/cc @aknappqwt @mmagyari