C API interface mismatch with gfortran 12.3.0

I'm getting some error in the C API when compiling using gfortran 12.3.0:

```
././src/minpack_capi.f90:442:20:

  442 |         call lmstr1(wrap_fcn, m, n, x, fvec, fjac, ldfjac, tol, info, ipvt, wa, lwa)
      |                    1
Error: Interface mismatch in dummy procedure ‘fcn’ at (1): INTENT mismatch in argument 'x'
```

A real error, or a compiler bug?
