[docs] Add a link to the regex module in re documentation (issue 22594)

[ezio.melotti at gmail.com]

http://bugs.python.org/review/22594/diff/13149/Doc/library/re.rst
File Doc/library/re.rst (right):

http://bugs.python.org/review/22594/diff/13149/Doc/library/re.rst#newcode47
Doc/library/re.rst:47: regex
Maybe this could be 'The "regex" module on PyPI'.

http://bugs.python.org/review/22594/diff/13149/Doc/library/re.rst#newcode48
Doc/library/re.rst:48: This is an alternative regular expressions module
with the following additional features among others in it's Version 1:
s/it's/its/ even though you might omit the last part, since it wasn't
obvious to me what Version 1 was before reading the PyPI page.

Maybe it should be mentioned somewhere that it's supposed to be a
drop-in replacement, with a mostly compatible API.

http://bugs.python.org/review/22594/diff/13149/Doc/library/re.rst#newcode50
Doc/library/re.rst:50: This occurs when the pattern consists only of
lookarounds,anchors or boundaries
Space after the comma, and additional comma after anchors.

http://bugs.python.org/review/22594/diff/13149/Doc/library/re.rst#newcode54
Doc/library/re.rst:54: * Full case folding support is enabled for
Unicode format
Only the first list element ends with a full-stop.  Either all or none
should have it.

These lines are also too long.

http://bugs.python.org/review/22594/