Add projects for MSVC 11 and 12 (MSVS 2012 and 2013).

Add manually created projects for now, as it looks that we are not going to
have bakefile-generated ones any time soon.

Closes #15780.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75926 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775