message: fix warnings in ImageCollection
diff: @@ -668,7 +668,7 @@ size_t imcount_(const String& filename, int flags)
  return collection.size();
  } catch(cv::Exception const& e) {
  // Reading header or finding decoder for the filename is failed
  - return 0;
  + std::cerr << "imcount_('" << filename << "'): can't read header or can't find decoder: " << e.what() << std::endl << std::flush;
  }
  return 0;
  }
  @@ -1141,7 +1141,7 @@ int ImageCollection::Impl::currentIndex() const { return m_current; }
  ImageCollection::iterator ImageCollection::Impl::begin(ImageCollection* ptr) { return ImageCollection::iterator(ptr); }
  -ImageCollection::iterator ImageCollection::Impl::end(ImageCollection* ptr) { return ImageCollection::iterator(ptr, this->size()); }
  +ImageCollection::iterator ImageCollection::Impl::end(ImageCollection* ptr) { return ImageCollection::iterator(ptr, static_cast<int>(this->size())); }
  void ImageCollection::Impl::reset() {
  m_current = 0;
  