Centralize standard getopts arguments, both for convenience and to correct
a bug in which certain combinations of arguments produced unexpected results
such as `-dX' (now properly produces debugging and X11), `-XS' (now properly
produces X11 in secure mode), `-df-' (enables debugging when reading a
script from standard-input, etc. Multi-word variations such as `-d -X',
`-X -S', `-d -f-', `-d -f -', etc. also work as expected. Also tested were
variations in argument order, which are now working as expected.