Without including wx/defs.h first, symbols such as __WXMSW__ are not defined if this header is the first wxWidgets header to be included. Closes #11718. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@63553 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775