Consistently naming anonymous structs

[Rhys Ulerich]

Anyone know how badly things break if we changed things like

typedef struct
  {
    const gsl_rng_type * type;
    void *state;
  }
gsl_rng;

to

typedef struct gsl_rng
  {
    const gsl_rng_type * type;
    void *state;
  }
gsl_rng;

so that some of our opaque types might be forward declared in C++ code?

- Rhys