Log Message:
(math/R-igraph) Updated 2.1.1 to 2.1.4

# igraph 2.1.4

## Testing

- Tweak tests that use the graph package.

# igraph 2.1.3

## Features

- Use `_pv` destroy functions to satisfy ASAN checks (#1630).

- Use safe accessor to vector elements (#1633).

## Chore

- Replace `graph.isomorphic()` with `isomorphic()` (#1583, #1623).

## Documentation

- Convert `plot.common.Rd` to roxygen2 (#1424, #1636).

- Remove broken example from `graph_from_graphdb()` manual page (#1622, #1637).

- Document argument for NCOL format in `read_graph()` (#1621).

- Make documentation of `disjoint_union()` consistent with behavior (#1587, #1641).

- Add central note about experimental functions (#1624).

# igraph 2.1.2

## Bug fixes

- `adjacent_vertices()` and `incident_edges()` are now correct if the
  `"return.vs.es"` option is `FALSE` (@stibu81, #1605, #1606).

- Fix protection errors reported by rchk (#1592).

- Fix the incorrect handling of the `sample` parameter in
  `sample_motifs()` and ensure that the default `sample.size` is
  integer (#1568).

## Documentation

- Clarify what type of graph each community detection function supports.

- Improve `?read_graph` and `?write_graph` documentation.

- Improve `all_simple_paths()` documentation.

- `cluster_optimal()` does support directed graphs.

## Testing

- Test handling of `"return.vs.es"` in several functions (@stibu81, #1610).