userlist: many new features and enhancements

Additional allowed options: qvhfwo

Also allows long options: verbose,colour,color,wrap,oneline,help

Added help()

Replaced references to "print" with "output".

Added verbose mode for a second line of extra info.
In verbose mode, header and user output can be shown on one line.

"double verbose" mode bolds the header.  Option for forcing this even if
STDOUT isn't a terminal.

Supports multiple users.

Streamlined passwd_crypt handling, i.e. all with the case statement, even
for empty crypts.

New Password state "locked-B".

Fixed option handling bug that ignored non-zero exit code from getopt.