* Silence warnings caused by duplicated defines from Modules\expat\winconfig.h
* Add WIN32 define to VS9.0 project files to match MSBuild project files.
The old project files move to PC/VS9.0 and remain supported.
VS2008 is still required to build 2.7; VS2010 (or later, plus Windows SDK 7.1)
is *also* required to use the new project files.