[docs] C code wrong after forward declaration

[Albert Zeyer]

Hi,

[Here](http://docs.python.org/library/ctypes.html#incomplete-types)
you have this C code:

struct cell; /* forward declaration */

struct {
    char *name;
    struct cell *next;
} cell;

It should be like this:

struct cell; /* forward declaration */

struct cell {
    char *name;
    struct cell *next;
};

Regards,
Albert