Merge branch 'feature/build' into feature/threads

Conflicts:
	src/mg/ppm_mg_init.f
	src/mg/ppm_mg_smooth_coarse.f
	src/mg/ppm_mg_smooth_fine.f
	src/mg/ppm_mg_solv.f
	src/ppm_define.h
	src/ppm_module_data_mg.f