Re: AC_PROG_F77 thinks my compiler is g77 (its not!)

[Akim Demaille]

Actually in the current case, GNUness should be tested in the
prologue, but in the body, which solves the current issue.

Still, what should we do out of the prologue for
AC_LANG_PROGRAM(Fortran 77)?  Still ignore it but warn when it's
nonempty?