Replace hand-rolled option parsing with the Getopt module. This is
shorter and easier to read. In passing, make some cosmetic adjustments
for consistency.

Author: John Naylor
Reviewed-by: David Fetter
Discussion: https://postgr.es/m/CACPNZCvRjepXh5b2N50njN+rO_2Nzcf=jhMkKX7=79XWUKJyKA@mail.gmail.com