Findewoms.cmake: fix typo

it's 'start.hh', not 'start.h'...
Catch up to opm-material reorganisation.

Specifically, file <opm/material/constants.hh> was renamed to
<opm/material/Constants.hpp> and this renaming must be reflected in
the CMake probes for opm-material.
Use dSYM bundles as debugging containers (on MacOS X)

gdb on MacOS X does not seem to be very fond of "flat" dSYM files, but
it can read the bundle variant fine. Thus we change that to enable
debugging across several tools.
Merge pull request #41 from bska/041_cmake

Synchronise build system with opm-core to restore debugging on MacOS X
Enable MPI if path is given

Assume that ./configure --with-mpi= also implies --enable-mpi; if you
absolutely want to specify path without enabling (?!) then you can do
--with-mpi=... --disable-mpi (in that order).

This patch look for anything after the equal sign of the --with
parameter and only set the variable _MPI_PREFIX_PATH if that is given;
it always toggle USE_MPI.
Merge pull request #42 from bska/042_cmake

Synchronise build system with opm-core
Merge branch 'master' of github.com:bska/opm-autodiff into eigen-3.2