[Patch, Fortran] Fix integer kind returned by storage_size

[Tobias Burnus]

Tobias Burnus wrote:
> The problem is fixed by the attached patch. I will commit it as 
> obvious (to the trunk, i.e. GCC 5 alias GCC 4.10 only) once building 
> and regtesting has finished.

As I only saw later in Steve's email, it is a regression. Thus, I will 
also apply it to the GCC 4.9 branch (will be in GCC 4.9.2; Linux distros 
likely pick it up earlier).

The regression was caused by my commit r197159 for PRs 56650 and 36437, 
which added compile-time simplification for storage_size, c_sizeof and 
sizeof. (The latter are not affected as they are supposed to return a 
value of kind c_size_t and take no kind parameters.)

Tobias