Use raw strings for regex patterns

[Harmon758]

Python 3.8.0b2 (tags/v3.8.0b2:21dd01d, Jul  4 2019, 16:00:09) [MSC v.1916 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import aiml
C:\Program Files\Python38\lib\site-packages\aiml\Kernel.py:1002: SyntaxWarning: invalid escape sequence \s
  elem[2] = re.sub("\s+", " ", elem[2])
C:\Program Files\Python38\lib\site-packages\aiml\PatternMgr.py:30: SyntaxWarning: invalid escape sequence \|
  punctuation = "\"`~!@#$%^&*()-_=+[{]}\|;:',<.>/?"
C:\Program Files\Python38\lib\site-packages\aiml\PatternMgr.py:32: SyntaxWarning: invalid escape sequence \s
  self._whitespaceRE = re.compile("\s+", re.UNICODE)

A backslash-character pair that is not a valid escape sequence generates a DeprecationWarning since Python 3.6. In Python 3.8 it generates a SyntaxWarning instead.

https://docs.python.org/3.8/whatsnew/3.8.html

Changed in version 3.6: Unrecognized escape sequences produce a DeprecationWarning.

Changed in version 3.8: Unrecognized escape sequences produce a SyntaxWarning. In some future version of Python they will be a SyntaxError.

https://docs.python.org/3.8/reference/lexical_analysis.html

https://bugs.python.org/issue32912, python/cpython#9652, python/cpython@6543912

[paulovn]

Thanks for this -- this is a leftover from the original 2.7 code