WIP: Move configure to m4
@matthieu: After a discussion with @pdraper, the simplest approach is to define m4 macros and just copy/paste them in PySWIFTsim.
In this merge request, I am just splitting configure.ac
in multiple files. I will deal with PySWIFTsim in a later merger request.
By the way, we cannot expand AC_PROG_FC
multiple time in a macro (required for velociraptor and grackle). The simplest approach was to have this requirement in every cases and not only with velociraptor/grackle. From my experience, fortran is still available on every linux computer.
Edited by Peter W. Draper