rm: raise error for long options

[mknos]

• I noticed that if I provide "long" options to rm, it gets confused and attempts to remove files starting with a dash
• When debugging this, preprocess_options() was incorrectly deciding to save long options into new_args list; call usage() instead because this rm only supports single letter options

  %perl rm --this    # before patch
  rm: cannot remove '-t': No such file or directory
  rm: cannot remove '-h': No such file or directory
  rm: cannot remove '-i': No such file or directory
  rm: cannot remove '-s': No such file or directory

[briandfoy]

changes: disable "long" options; single letter options only