rolld - Roll the three top stack elements downward
obj1 obj2 obj3 rolld -> obj2 obj3 obj1
rolld is equivalent to 3 -1 roll
Raises StackUnderflow error if there are less
than 3 objects on the stack.
/builddir/build/BUILD/nest-simulator-3.3/nest-simulator-3.3/sli/slistack.cc