struct clone fixed.

struct clone fixed.

* A struct cloned must have all SingleStruct reference set to 1
  because we cant increase reference of SingleStruct when we do it
  on a Struct.

z.y = 42;
y.o = z;

// here z is cloned, after extraction of z(1), two Struct
// contain the same SingleStruct with ref = 1 because of extraction without copy.
// When the temporary Struct "z(1)" is deleted, the SingleStruct is deleted too.
z(1).x=12;

Change-Id: I3b90752cdae7cdfe172bed30d8ad67959dc787f6