This will be useful for allowing other projects, not necessarily located at
the same level of the file hierarchy as the projects for building the library,
to refer to the location of the libraries more easily.
Get rid of version-specific MSVS project files, we can reuse the same projects
for all MSBuild-based versions, i.e. 2010, 2011 and 2013.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77008 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
