[3.4] bpo-31170: Fix inclusion of expat in Windows build projects (#3785)

[3.4] bpo-31170: Fix inclusion of expat in Windows build projects (#3785)

* bpo-31170: Fix inclusion of expat in Windows build projects

Co-Authored-By: Steve Dower <steve.dower@microsoft.com>
* expat: Fix compilation on Visual Studio 2010

The standard header stdbool.h is not available
with old Visual Studio compilers

Cherry-picked from libexpat commit b4b89c2ab0cc5325a41360c25ef9d2ccbe617e5c.

expat: Add artificial scopes in xmltok.c utf8_toUtf8() to fix c89 compilation.

Cherry-picked from libexpat commit e0b290eb3d8f4c4b45137a7d7f4f8db812145bd2

* Expat: fix preprocessor defines in VS projects

Remove the following defines:

* BYTEORDER=1234
* HAVE_MEMMOVE
* USE_PYEXPAT_CAPI
* XML_CONTEXT_BYTES=1024
* XML_DTD
* XML_NS
* XML_STATIC

* PCbuild/pyexpat.vcxproj: define _CRT_SECURE_NO_WARNINGS