Parse short options in order given

Fixes:
* Short options cannot be repeated in the same group: e.g., `-nn` fails
* Short options are processed in an arbitrary fixed order, not the order
  given by the user: e.g., both `-hV` and `-Vh` are processed as `-h`
* `-L` cannot be a part of a short option group (as the last one):
  e.g., `-nLlib` and `-nL lib` fail