fortran support finally back in base - please test

hi folks.


20 years ago when gcc 4 came out, g77 was replaced by gfortran and
it had some issues and we dropped it.  finally, it's back.  i think
i've got it working for all platforms, but it needs a lot more
testing from real fortran users before i'd consider it stable.
once it's stable, maybe pkgsrc can start to use it instead of
having to install gcc12 pkg for it.. (this part may take a while,
and i'm not sure how it needs to be done anyway.)

let me know (here, send-pr are best) if you have success or
failure with it.

thanks.


.mrg.