This commit adds support for a type of command-line options that are
commonly used by many GNU tools. Now with this modification if you
have an option named 'verbose' with an integer argument and you enter
"-vvv" as in the command line you'll get {verbose, 3} as a result.
Add support for short options with embedded arguments (e.g. -j2).
Add support for implicit boolean options (e.g. -q -> {quiet, true}).
Add support for option terminator ("--").
