Improve comments.

This patch adds test for both CMake and autotools as the
build system.
UMFPack is used by several dune modules (e.g. fem and istl)
the only common required module by both is common. Therefore
we add the test here to make it usable for all modules.

BTW: These tests are taken from Dominics branch of dune-istl.
     Therefore he deserves the credit for them.