getopt(1) emulator: Introduce option properties
getopt(1) emulator: Introduce option properties

Instead of controlling option parsing with lots of local variables and
function parameters, we introduce per-pass option properties kept in
global array piow2ov[PI,OW], where
  - PI is the affected pass' index and
  - OW is (wherever possible) the respective short option's word (i.e.,
    the short options's name sans leading '-').

Our first candidate is option -a|--alternative, where piow2ov[PI,"a"] is
a boolean indicating if alternative long options are allowed.

Consequently,
  - args_getopt()'s local variable alternative as well as
  - getopt_next()'s parameter alternative
are dropped.

donkarlos/libdl-sh