Roll back the introduction of urlsplit() and urlunsplit() to

Roll back the introduction of urlsplit() and urlunsplit() to
urlparse.py.  These were new features in 2.2, and shouldn't be added
to 2.1 this late in the game.  There was one use of urlsplit() in
httplib.py (the urlparse.py change was done as part of a backport of a
bugfix to httplib.py); this use is replaced with a call to urlparse()
without changing the effect (only the returned netloc is used).