// returns number of calls removed
static int dropFunctionCalls_reTok(LS tok, S functionName) {
  int removed = 0;
  while true {
    var r = tok_findFunctionCall(tok, functionName);
    if (r != null) {
      clearTokens_reTok(tok, r);
      ++removed;
    } else
      break;
  }
  ret removed;
}