Add explicit lint-comment-style fallthrough annotations. GCC now assumes that if you don't have these you're making a mistake, which is annoying. XXX: This changeset updates the AG output files only (by hand) and is XXX: abusive - rebuilding them will erase the change. However, I need XXX: to get things to build before I can try to get AG to issue the XXX: annotations itself, so this seems like a reasonable expedient.

struct buffer {
  char *text;
  size_t len;
  size_t allocsize;

  /* structural invariant: text[len]==0 */
};

void buffer_init(struct buffer *);
void buffer_cleanup(struct buffer *);

void buffer_append(struct buffer *, const char *);
void buffer_add(struct buffer *, int ch);
void buffer_start(struct buffer *, int ch);
void buffer_clear(struct buffer *);