Returns an InstructionHandle to the physical successor
of this JsrInstruction. For this method to work,
this JsrInstruction object must not be shared between
multiple InstructionHandle objects!
Formally, there must not be InstructionHandle objects
i, j where i != j and i.getInstruction() == this ==
j.getInstruction().
Returns:
an InstructionHandle to the "next" instruction that
will be executed when RETurned from a subroutine.