[docs] Improve cross-references in pickle documentation. (issue 19189)

[georg at python.org]

http://bugs.python.org/review/19189/diff/9465/Doc/library/pickle.rst
File Doc/library/pickle.rst (right):

http://bugs.python.org/review/19189/diff/9465/Doc/library/pickle.rst#newcode394
Doc/library/pickle.rst:394: calling :meth:`~.object.__getstate__` is
picklable  (see section
~object. should never be needed for methods.

These appear to be false positives.

http://bugs.python.org/review/19189/