message: Rewrite bsoncxx::document::view::find() to avoid string allocation
diff: @@ -125,12 +125,19 @@ view::const_iterator view::find(stdx::string_view key) const {
  return cend();
  }
  - if (!bson_iter_init_find(&iter, &b, key.to_string().data())) {
  + if (key.empty()) {
  return cend();
  }
  + while (bson_iter_next(&iter)) {
  + const char* ikey = bson_iter_key(&iter);
  + if (0 == strncmp(key.data(), ikey, key.size())) {
  return const_iterator(element(iter.raw, iter.len, iter.off));
  }
  + }
  +
  + return cend();
  +}
  element view::operator[](stdx::string_view key) const {
  return *(this->find(key));
  