(Merge 3.4) Issue #20879: Delay the initialization of encoding and decoding

tables for base32, ascii85 and base85 codecs in the base64 module, and delay
the initialization of the unquote_to_bytes() table of the urllib.parse module,
to not waste memory if these modules are not used.

diff --cc Misc/NEWS
index 55887b70df3634269a5a69e3e3bf2240e879424c,33e7092af1721ab02c7a1a9871c09ef0a426b920..f6ae02c02f9e4c0aece99c17915a2c1ae47c4d1d
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -13,6 -13,71 +13,11 @@@ Core and Builtin
  Library
  -------
  
 -- Issue #19157: Include the broadcast address in the usuable hosts for IPv6
 -  in ipaddress.
 -
 -- Issue #11599: When an external command (e.g. compiler) fails, distutils now
 -  prints out the whole command line (instead of just the command name) if the
 -  environment variable DISTUTILS_DEBUG is set.
 -
 -- Issue #4931: distutils should not produce unhelpful "error: None" messages
 -  anymore.  distutils.util.grok_environment_error is kept but doc-deprecated.
 -
 -- Issue #20875: Prevent possible gzip "'read' is not defined" NameError.
 -  Patch by Claudiu Popa.
 -
 -- Issue #11558: ``email.message.Message.attach`` now returns a more
 -  useful error message if ``attach`` is called on a message for which
 -  ``is_multipart`` is False.
 -
 -- Issue #20283: RE pattern methods now accept the string keyword parameters
 -  as documented.  The pattern and source keyword parameters are left as
 -  deprecated aliases.
 -
 -- Issue #20778: Fix modulefinder to work with bytecode-only modules.
 -
 -- Issue #20791: copy.copy() now doesn't make a copy when the input is
 -  a bytes object.  Initial patch by Peter Otten.
 -
 -- Issue #19748: On AIX, time.mktime() now raises an OverflowError for year
 -  outsize range [1902; 2037].
 -
 -Documentation
 --------------
 -
 -- Issue #20765: Add missing documentation for PurePath.with_name() and
 -  PurePath.with_suffix().
 -
 -- Issue #19407: New package installation and distribution guides based on
 -  the Python Packaging Authority tools. Existing guides have been retained
 -  as legacy links from the distutils docs, as they still contain some
 -  required reference material for tool developers that isn't recorded
 -  anywhere else.
 -
 -Tests
 ------
 -
 -- Issue #20743: Fix a reference leak in test_tcl.
 -
 -Tools/Demos
 ------------
 -
 -- Issue #20535: PYTHONWARNING no longer affects the run_tests.py script.
 -  Patch by Arfrever Frehtes Taifersar Arahesis.
 -
+ - Issue #20879: Delay the initialization of encoding and decoding tables for
+   base32, ascii85 and base85 codecs in the base64 module, and delay the
+   initialization of the unquote_to_bytes() table of the urllib.parse module, to
+   not waste memory if these modules are not used.
+ 
  
  What's New in Python 3.4.0?
  ===========================