When profiling the GPU version, NVTX can be used to highlight the
corresponding regions of the code in the timeline of the profiling tool
(nvvp or nsight systems). This is very useful to correlate what happens
on the GPU with what part of the code we are in.

Seperate the variable type definition of the library and the test programs

See merge request !21

Auto detect

See merge request !20

On heterogenous cluster, of nodes with different CPUs the _experimental_
feature (--enable-heterogenous-cluster-support) can be used:

It compares the (Intel) cpuid set of all CPUs which are used by ELPA MPI
processes and finds the SIMD instruction set, which is supported by all
used CPUs. The ELPA 2stage back-transformation kernel (a.k.a "kernel")
will be set accordingly on all MPI processes.

This feature, can override the setting of the kernel done previously by
the user!

At the moment it will only work for Intel CPUs, i.e. clusters consisting
of nodes with Intel CPUs and e.g. AMD CPUs are at the moment _NOT_
supported.

Since this is an experimental feature, it might be dropped again in the
future, if it turns out not to be useful for the users

This release just additionally packages the src files from the legacy interface,
which had been forgotten in the previous release

Obviously, recent versions of automake decided to filter out
an "test_" string which led to some surprises