[gfortran] patch for PR libfortran/24903

[FX Coudert]

> Attached patch fixes PR libfortran/24903: we used to separately assign 
> real and imaginary parts of a complex instead of simply using 
> __builtin_conj{f,,l}.
>
> Bootstrapped and regested on i686-linux. OK for trunk?

ping. i have to say i'm very tempted to say i'll commit it during the 
week-end if nobody has objection. i'll probably send another warning 
before I do, though :)

FX