[docs] Improve cross-references in shlex documentation (issue 19197)

[georg at python.org]

http://bugs.python.org/review/19197/diff/9477/Doc/library/shlex.rst
File Doc/library/shlex.rst (right):

http://bugs.python.org/review/19197/diff/9477/Doc/library/shlex.rst#newcode27
Doc/library/shlex.rst:27: (setting the :attr:`~shlex.shlex.commenters`
attribute of the
for all attributes, `~shlex.commenters` etc. should be enough.

http://bugs.python.org/review/19197/