Update the embedded copy of the expat XML parser to 2.1.0.  It brings
with it a vareity of bug fixes, both security and behavior.  See
http://www.libexpat.org/ for the list.

NOTE: I already backported the expat hash randomization fix in March.

Fixes issue #14340.
Issue #16485: Fix file descriptor not being closed if file header patching fails on closing of aifc file.
Fix docstring in curses (#16782)
Issue #16645: Fix hardlink extracting test for tarfile.
Fix issue 10527: make multiprocessing use poll() instead of select() if available.
Issue #14958: backport to 2.7.x from 3.3 (patch by Roger Serwy)
bring Python into 2013
merge heads
update another year
Issue #9586: Redefine SEM_FAILED on MacOSX to keep compiler happy.
Update copyright dates in Mac plists.
Issue #16819: IDLE method completion now correctly works for unicode literals.
get the core to compile --disable-unicode
Fix incorrect grammar in Misc/NEWS.
Fix method name in documentation (__setstate__ --> __getstate__)
ensure the attribute name string is initalized before using it (closes #16839)
merge heads
call PyErr_Clear() when ignoring error from PyNumber_Int (closes #15516)

Patch from Tom Tromey.
add Tom Tromey to ACKS
untabify