optparse: Various enhancements.

  * General cleaning up.

  * Removal of redundant handling of option docstrings in both options
    macro and parse-option-form.

  * New feature: option macros can insert several options.

  * New suite of standard option-handling things for usual command-line
    programs.  Should be sufficient for most purposes.  I'll probably
    invent a subcommand system later when I get a feel for what's
    wanted.