[gfortran,patch] Add ISO_FORTRAN_ENV module

[FX Coudert]

> This assumes that the integer kinds are equal to the size in bytes  
> of the integer.  Is this always true?  [Answer to my own question:  
> Currently, yes; see line 121 of trans-types.c.]

Well, I can't answer to a question that was already answered :)

> However, I do see that there is a .bit_size field in  
> gfc_integer_kinds; I think it would probably be a little cleaner to  
> use this rather than back-calculating the bit size from the kind  
> number.

OK, please consider that change taken into account.

FX