arpackmm: utility to test arpack with matrix market files.

This is meant to run arpack with different options to find
what are the ones that are the best for your particular
problem.

Typically: computing small eigen values may breakdown and/or
be slow (arpack is good at finding large eigen values only).
To compute small eigen values, it may be a better choice
to look for large eigen values with invert or shift+invert.

If solve breaks down, you may increase --nbCV, try --restart,
play with --shiftReal/Imag and/or --invert.

To build this utility, you need:
- to use a fortran compiler which supports iso_c_binding.
- to have installed eigen3 (to deal with the RCI).
- to configure arpack-ng this way:
  - autotools:
    ~arpack-ng> ./configure --enable-icb-exmm; make all check
  - cmake:
    ~arpack-ng/build> cmake -D ICBEXMM=ON ..; make all test