Add `make_hypercube()`

[szhorvat]

Expose igraph_hypercube(). Suggested R name: make_hypercube(). Don't forget to also add the corresponding hypercube(), which can be used with make_().

When writing docs, please pay attention to the phrasing zero-based vertex ID in the C docs. What's stated there is not true once IDs are shifted to be one-based.