solve SyntaxWarning: invalid escape sequence '\s' errors

[adamhotep]

Solves the following errors:

/usr/share/rlwrap/filters/ftp_filter.py:57: SyntaxWarning: invalid escape sequence '\s'
  results = [re.split('\s+', l)[dir_filename_column[where]] for l in lines]
/usr/share/rlwrap/filters/ftp_filter.py:100: SyntaxWarning: invalid escape sequence '\s'
  nwords = len(re.split('\s+', line))
/usr/share/rlwrap/filters/ftp_filter.py:108: SyntaxWarning: invalid escape sequence '\s'
  command = re.search('\s*(\S+)', line).group(1)
/usr/share/rlwrap/filters/rlwrapfilter.py:4: SyntaxWarning: invalid escape sequence '\s'
  """
/usr/share/rlwrap/filters/rlwrapfilter.py:211: SyntaxWarning: invalid escape sequence '\S'
  m = re.match("(\S+) (.*?)\r?\n", sys.stdin.readline())

Pass regexes to re.split and re.match, escape the \s instances in the """ documentation. (Some of the changed calls were fine as strings, but this introduces consistency and future-proofs them in the event they change.)