This allows for `make distclean` (subdirs) in old automake versions.

However, they are still commented (not compiled).

Allows for make uninstall.

Set automatically to MPI if CC=mpi*

The user can specify or not the path to OFED.

There is no need for copy and/or use the external macro
for the module flag.

External macros has been copied into config/

The (doxygen) documentation and the tutorial code are built through `make docs` and
`make tutorial`, respectively.