ui/lc.scm (print-help): Rename to `print-help-and-exit'.

* ui/lc.scm (print-help): Improve.  Rename to `print-help-and-exit'.
  Call `exit'.  All callers updated.
  (main): Update.
ui/cli/format-table.scm (get-padding-from-fmt): Improve.
ui/cli/format-table.scm (cut, rest): Improve error checking.
ui/cli/format-table.scm (format-table): Improve.