Merge doc fixes from 3.5

diff --cc Doc/library/logging.handlers.rst
Simple merge

diff --cc Doc/library/socket.rst
Simple merge

diff --cc Doc/library/unittest.rst
Simple merge

diff --cc Doc/whatsnew/2.1.rst
Simple merge

diff --cc Misc/NEWS
Simple merge

diff --cc Modules/_collectionsmodule.c
Simple merge

diff --cc Modules/_io/textio.c
Simple merge

diff --cc Objects/odictobject.c
Simple merge