void freeze;
ByteString frozen;
protected id init (pointer, int) (p, num);
id initCopy (pointer, int) (p, num);
super does, adjust our (new) capacity to
fit our length.
void set char c at int index;
index to the character c, converted to a byte
according to the default_encoding.
void add char c;
char c to this string.
ByteString substring (int, int) (start, len);
ByteString implementation of this substring method,
since that actually employs ByteSubstring objects which we can't
use.