sci-libs/m4rie: new package for matrices over GF(2^e) with "e" small.

sci-libs/m4rie: new package for matrices over GF(2^e) with "e" small.

The m4rie package is an extension of sci-libs/m4ri. It is used by
SageMath, which can now detect and use the system copy of m4rie. Its
inclusion therefore prevents pointless rebuilds of m4rie by users of
SageMath on Gentoo. The ebuild was imported from the sage-on-gentoo
overlay where François Bissey has been maintaining it.

Closes: https://bugs.gentoo.org/711498
Package-Manager: Portage-2.3.84, Repoman-2.3.20
Signed-off-by: Michael Orlitzky <mjo@gentoo.org>