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 #17106: Fix a segmentation fault in io.TextIOWrapper when an underlying
stream or a decoder produces data of an unexpected type (i.e. when
io.TextIOWrapper initialized with text stream or use bytes-to-bytes codec).
Issue #17106: Fix a segmentation fault in io.TextIOWrapper when an underlying
stream or a decoder produces data of an unexpected type (i.e. when
io.TextIOWrapper initialized with text stream or use bytes-to-bytes codec).
Issue #17106: Fix a segmentation fault in io.TextIOWrapper when an underlying
stream or a decoder produces data of an unexpected type (i.e. when
io.TextIOWrapper initialized with text stream or use bytes-to-bytes codec).
pyexpat/xml.parsers.expat create their errors and model modules from
scratch. This means they do not set __loader__ by default. This is
acceptable under importlib/PEP 302 definitions, so relax the test that
was trying to apply this universally.
merge
merge
merge
merge
null merge
null merge
Way too many places create modules temporarily that never set
__loader__ for this test to succeed without a major changes. It also
doesn't test the original issue of modules imported by Py_Initialize()
having __loader__ set (the rest of the test covers that).
merge w/ 3.3
fix find_library on Solaris (closes #5289)
merge 3.3 (#5289)
Minor edits:  Tighten-up the halflen logic and touch-up the assertions and comments.
Issue #6083: Fix multiple segmentation faults occured when PyArg_ParseTuple
parses nested mutating sequence.
Issue #6083: Fix multiple segmentation faults occured when PyArg_ParseTuple
parses nested mutating sequence.
Issue #6083: Fix multiple segmentation faults occured when PyArg_ParseTuple
parses nested mutating sequence.
Temporarily disable test_from_dll in test_returnfuncptrs.py for Windows.