How to handle nested structs when converting C headers?

[Gary Willoughby]

How to handle nested structs when converting C headers?

In the following snippet i'm currently converting, how would you 
convert the nested typed union and structures? Would you declare 
them separately then use their types in the Tcl_Obj struct? or is 
there a nice way in D to nest them like C?

typedef struct Tcl_Obj {
     int refCount;		/* When 0 the object will be freed. */
     char *bytes;		/* This points to the first byte of the
				 * object's string representation. The array
				 * must be followed by a null byte (i.e., at
				 * offset length) but may also contain
				 * embedded null characters. The array's
				 * storage is allocated by ckalloc. NULL means
				 * the string rep is invalid and must be
				 * regenerated from the internal rep.  Clients
				 * should use Tcl_GetStringFromObj or
				 * Tcl_GetString to get a pointer to the byte
				 * array as a readonly value. */
     int length;			/* The number of bytes at *bytes, not
				 * including the terminating null. */
     Tcl_ObjType *typePtr;	/* Denotes the object's type. Always
				 * corresponds to the type of the object's
				 * internal rep. NULL indicates the object has
				 * no internal rep (has no type). */
     union {			/* The internal representation: */
	long longValue;		/*   - an long integer value. */
	double doubleValue;	/*   - a double-precision floating value. */
	VOID *otherValuePtr;	/*   - another, type-specific value. */
	Tcl_WideInt wideValue;	/*   - a long long value. */
	struct {		/*   - internal rep as two pointers. */
	    VOID *ptr1;
	    VOID *ptr2;
	} twoPtrValue;
	struct {		/*   - internal rep as a wide int, tightly
				 *     packed fields. */
	    VOID *ptr;		/* Pointer to digits. */
	    unsigned long value;/* Alloc, used, and signum packed into a
				 * single word. */
	} ptrAndLongRep;
     } internalRep;
} Tcl_Obj;