igraph

Changed igraph_write_graph_pajek(): the function now always uses the platform-native line endings (CRLF on Windows, LF on Unix and macOS). Earlier versions tried to enforce Windows line endings, but this was error-prone, and since all recent versions of Pajek support both line endings, enforcing Windows line endings is not necessary any more. Fixed Fixed several compilation issues with MINGW32/64 (PR #1554) igraph_layout_davidson_harel() was not interruptible; now it is. Added a missing memory cleanup call in igraph_i_cattribute_combine_vertices(). Fixed a few memory leaks in test cases