spline: use evalDerivative_() instead of evalDerivative() if the segment index is known

thanks to @bska for catching this!
spline: actually return something in evalDerivative() in the extrapolate case

once more, thanks to @bska to catching this!
Merge pull request #394 from andlaus/fix_spline_monotonic

Spline: fix a few issues with the monotonic() methods
Instructions on how to build prerequisites on MacOS X

Although it is possible using the GNU toolchain, there is
probably a larger base which has the Apple toolchain and want to
use that.
Remove unused "typedef"s

CLang and recent versions of GCC warn about unused "typedef"s.  This
change-set removes currently known instances in opm-core.
Merge pull request #396 from bska/resv-injectors

Tentative solution to problem of RESV injectors in `ifs_tpfa.c`
Merge pull request #399 from rolk/399_macosx

Add instructions on how to build prerequisites on MacOS X
Merge pull request #400 from bska/Wunused

Remove unused "typedef"s
Merge pull request #395 from bska/nullptr-deref

Fix null-pointer dereference during well construction
Remove unneeded term, fixing oil injecting behaviour.

The 'comp_term' is supposed to be a total divergence term, which is supposed
to be zero for incompressible flow. It was added for improved robustness in
stagnant areas, but as implemented it would not be computed properly for
oil injection scenarios, due to the convention for two-phase transport
source terms (positive terms are inflow of first phase [water], negative
terms are total outflow).
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 #402 from rolk/401_dsym

Use dSYM bundles as debugging containers (on MacOS X)
Merge pull request #401 from atgeirr/fix-oilinjection

Fix oil injecting behaviour of TransportSolverTwophaseReorder.
Merge pull request #386 from totto82/propsMRST

Changes to the props in order to  sync with MRST (Eclipse)
Guard against erroneous use of initBlackoilSurfvol().
Modify error message.
Merge pull request #404 from atgeirr/fix-initblackoilsurfvol

Guard against erroneous use of initBlackoilSurfvol().
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 #405 from rolk/405_mpi

Enable MPI if path is given
Pass BUILDNAME and SITE options along to CTest/CDash

By passing these options through ./configure, one can use dunecontrol
to build a complete stack and still get a customized description in
CDash (such as when building in a cluster or VM where the actual machine
name does not matter, or when you want to add key options to the name
shown) without having to run a second configuration just to set those
in the cache.

Also fixes a bug where --with-cmake would skip any further option
specified after it.