sci-mathematics/rw: new revision sans the "rw" executable.

sci-mathematics/rw: new revision sans the "rw" executable.

The main use case for rw is as a library, specifically one used by
SageMath. The "rw" executable was nice to have, but it pulls in
dev-libs/igraph, and igraph upstream has gone crazy and started
copy/pasting libraries into its "src" directory. Since igraph
will never be upgraded like that, it's staying unmaintained and
won't be stabilized, thereby blocking the stabilization of rw.

This commit drops the "rw" executable entirely, so that we can get rid
of the igraph dependency and stabilize a version of rw.

Package-Manager: Portage-2.3.84, Repoman-2.3.20
Signed-off-by: Michael Orlitzky <mjo@gentoo.org>