[Patch, Fortran] Implement F2008's c_sizeof (PR36437)

[Jerry DeLisle]

Tobias Burnus wrote:
> This patch implements Fortran 2008's C_SIZEOF, which is a one liner. It 
> additionally does:
> - Add documentation (essentially a copy from SIZEOF)
> - Fix keyword= should be x= and not i=
> - Simplify the generated tree. For scalars gfortran produced:
> 
>  {
>    integer(kind=8) bytes.1;
>    i = 4;
>  }
> 
>  and now it simpy generates:   i = 4;
> 
> Build and "make check-gfortran pdf html" tested on x86-64-linux. OK for 
> the trunk?

OK,

Jerry