[fortran] Disable use of -malign-double

[FX Coudert]

> At the risk of being a rebel I agree with Erik on this point.  It  
> does not hurt anything to inoculate libgfortran, it is not  
> difficult to do, and it makes no statement about whether people do  
> or do not use the option. Even if the inoculation is not perfect,  
> things are no worse then they are now.

I'd agree with you, but I have two remarks:
   1. what is the effect of the libgfortran ABI change involved in  
terms of performance?
   2. I 'm not sure we can port that change in 4.2 (if the problem  
exists there, that is)

> It also makes no statement regarding compatibility or  
> incompatibility with other libraries.  User beware.

Of course.

> I also like Manuel's idea of -Wabi as a default.  If g++ is already  
> doing this, why not borrow that.

Same thing here. Looks like we are converging on something. Any other  
opinions before we file a PR with a sum-up of the discussion?

FX