over - Copy object at stack level 1
any obj over -> any obj any
1 2 3 over -> 2
1 2 3 4 5 over -> 4
Raises StackUnderflow error if there are less than two objects on
the stack.
/home/abuild/rpmbuild/BUILD/nest-2.20.git-build/nest-2.20.git/sli/slistack.cc