// tok must come from htmlTok
// returns index of closing tag or l(tok)
static int findClosingTag(LS tok, int iOpeningTag) {
  S tag = getTag(tok.get(iOpeningTag));
  int level = 1;
  for (int i = iOpeningTag+2; i < l(tok); i += 2) {
    S t = tok.get(i);
    if (eqic(getTag(t), tag)) {
      if (isClosingTag(t))
        --level;
      else
        ++level;
      if (level == 0)
        ret i;
  }
  ret l(tok);
}