I modified my working 0.3 (from the tar gz now available online), such that get.adjacency can also return a Laplacian matrix. This is a trivial change (although I hope I didn't mess it up), and I am attaching the associated changes to this mail.
In this process:
conversion.c igraph.h conversion.R conversion.Rd
had to be modified.
This feature is relevant to me but I don't know if it is to others. Gabor you are more than welcome to include it if you deem it correct (: and relevant
adding_laplacian