[gfortran,patch] add ISO_FORTRAN_ENV intrinsic module

[FX Coudert]

> Thanks for the details.  I was wondering why your -fintrinsic-module
> option required a user to specify a path.  I now see that the module
> must match its library and the multilib feature means multiple  
> modules.

I'll note that, -fintrinsic-module can be specified by the user, it's  
mainly used by the specs to tell the compiler where the multilib- 
specific pre-compiled modules are. I'm not sure if it was clear in my  
submission mail.

FX