fortran: note there is no has_function for Fortran
fortran: note there is no has_function for Fortran

It would be very challenging if not futile to make has_function work for Fortran.
The meson.get_compiler('fortran').links() works very well instead.
As a reference, CMake's check_fortran_function_exists is completely broken in general.

This change raises a useful MesonException instead of giving bizarre errors.

QuLogic/meson,pexip/meson,becm/meson,QuLogic/meson,pexip/meson,becm/meson,QuLogic/meson,pexip/meson,jpakkane/meson,mesonbuild/meson,jpakkane/meson,QuLogic/meson,jpakkane/meson,mesonbuild/meson,pexip/meson,becm/meson,jpakkane/meson,mesonbuild/meson,mesonbuild/meson,becm/meson,pexip/meson,becm/meson,QuLogic/meson,QuLogic/meson,becm/meson,QuLogic/meson,jpakkane/meson,pexip/meson,jpakkane/meson,mesonbuild/meson,becm/meson,becm/meson,pexip/meson,jpakkane/meson,mesonbuild/meson,jpakkane/meson,QuLogic/meson,QuLogic/meson,pexip/meson,becm/meson,mesonbuild/meson,pexip/meson,mesonbuild/meson,becm/meson,jpakkane/meson,pexip/meson,mesonbuild/meson,mesonbuild/meson