Streaming Gz module gives incorrect results

Imported from http://bugzilla.roxen.com/bugzilla/show_bug.cgi?id=885

Reported by Fredrik Noring, Roxen Internet Software noring@roxen.com

The following code trigs a bug:

string data0 = ...; // 66560 characters. string data1 = ...; // 66560 characters.

   function gzd = Gz.deflate()->deflate;
   function gzi = Gz.inflate()->inflate;

   int main()
   {
     string packed = "";

     packed += gzd(data0, Gz.NO_FLUSH);
     packed += gzd(data1, Gz.NO_FLUSH);
     packed += gzd("", Gz.FINISH);

     return !(data0 + data1 == gzi(packed));
   }

The complete source code is available at:

Pike/7.1/src/modules/Gz/flushtest.pike