4.16.0

- Focus must not be required in single click mode (Issue #190)
- Remove GLIB_CHECK_VERSION IFDEFs which are obsolete after glib bump
- Adjust padding only for vertical item orientation (Issue #48)
- bump glib (and gio, gthread, etc) to 2.50.0
- Fix GCC warning (false negative)
- Translation Updates:
  Basque, Estonian, Norwegian Bokmål, Portuguese (Brazil), Russian,
  Slovenian, Turkish, Vietnamese