Add mpe2 to overlay

This adds MPE (MPI Parallel Environment) to the overlay:
* version bumped from 1.0.6p1 to 1.3.0
* EAPI was updated from 2 to 5, gentoo bug #478562
* missing die(s) were added
* HOMEPAGE fixed
Just set in src_prepare()

MAKEOPTS+=" -j1",

then you don't need to add it to every make