the csh -b, permitting more options to be stacked after it and
take effect. Make -b take effect depending on SH_OPTION_LETTERS,
consistent with all the other single-letter options, rather than
having a clashing check of emulation type.
Src/zsh.mdd: Allow options to be specified on the zsh command line
in the form of GNU-style long options. Also handle --version
and --help. Do not permit extra option letters to be stacked
after `-whatever-' (they used to be ignored). Exit if the
command line specifies an option name that doesn't exist.
