Add preprocessor flag include_mpi

 - Allows to use MPI by "include mpif.h" instead of "use mpi".
 - Kind of a hack, but otherwise running the code is not possible on machines with more than one version of gfortran installed. Also applies to other compilers sometimes, when openmpi was not compiled with exactly the same version
makemake.pl ignores include in .f90 files

 - To avoid an entry for mpif.h
 - In case somebody wants to use a 'include' in this Fortran2003 code, please mail me
Merge branch 'master' of https://github.com/geodynamics/axisem into HEAD

Conflicts:
	SOLVER/Makefile.TEMPLATE
Merge branch 'master' of https://github.com/geodynamics/axisem