Expose `igraph_is_clique()` and `igraph_is_independent_vertex_set()`. I suggest the `is_clique()` and `is_ivs()` names in R. Related: #1316
Expose
igraph_is_clique()andigraph_is_independent_vertex_set(). I suggest theis_clique()andis_ivs()names in R.Related: #1316