A new framework in support of multiple MPI implementations

There are numerous MPI implementations in the Gentoo portage tree and far more in general, but most of them can't be installed together as is. The only way to do this now is by using empi from the science overlay and empi has its shortcomings such as lack of multilib support and was not ported to the main tree. In my proposed plan, a new MPI framework ported from existing MPI applications is introduced to enable Gentoo to use multiple MPI versions and relevant packages depending on them (for example, HPL). The new MPI framework is mainly based on ‘Modules’ package together with Gentoo Prefix technique for detecting, choosing or manipulating MPI environment. Also, a new implementation of mpi.eclass is introduced and the packages can still be emerged normally onto the system without any trace of mpi.eclass being used. The approach also enables users to easily work with different implementations at the same time without any special privileges. In order to solve the defect that empi does not support multilib, the new framework also adds support for allowing the environment to be configured and installed into different places among different architectures (amd64, x86 etc.).