PETSc: copy an ebuild from Gentoo Science Overlay (https://github.com/gentoo-science/sci).
Make PETSc installation directories more close to the default installation.
PETSc: install files needed by a python wrapper.
PETSc: disable the invocation of petscnagupgrade.py.
PETSc: improve Python dependencies.
Add petsc4py, a Python wrapper for PETSc.
SLEPc: copy an ebuild from https://github.com/joshuar/MSI-Cluster-Gentoo-Overlay.
SLEPc: update ebuild.
USE=python for petsc is not required by petsc4py.
PETSc: install Fortran files properly.
SLEPc: install Fortran files properly.
SLEPc: change only -j option for make.
SLEPc: remove unnecessary dependency on petsc4py.
SLEPc: fix RDEPEND and DEPEND variables.