Merge fix for #18805 from 3.3

diff --cc Lib/ipaddress.py
Simple merge

diff --cc Lib/test/test_ipaddress.py
Simple merge

diff --cc Misc/NEWS
index 998d87c8f84383110cad3252087d9a8ea7e557c2,4df6c23682fc18cd81191e6bff07789276e50e8c..92d668ca99a6e6774fae125156908f249ea11f95
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -27,15 -48,9 +27,18 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #18805: the netmask/hostmask parsing in ipaddress now more reliably
+   filters out illegal values
+ 
 +- Issue #20481: For at least Python 3.4, the statistics module will require
 +  that all inputs for a single operation be of a single consistent type, or
 +  else a mixed of ints and a single other consistent type. This avoids
 +  some interoperability issues that arose with the previous approach of
 +  coercing to a suitable common type.
 +
 +- Issue #20478: the statistics module now treats collections.Counter inputs
 +  like any other iterable.
 +
  - Issue #17369: get_filename was raising an exception if the filename
    parameter's RFC2231 encoding was broken in certain ways.  This was
    a regression relative to python2.