prolog::rb_del_min/4

I am afraid our representation is not as nice for delete%.

rb_del_min(+ Tree,- Key,- Val,- TreeN)*

Delete the least element from the tree Tree, returning the key Key, the value Val associated with the key and a new tree TreeN.

Private-func:

1. prolog::rb_del_min_4::rb_del_min/4(int ARG1, int ARG2, int ARG3, int ARG4)():