Remove MSW wxUxThemeEngine class

This undocumented "private" class was used for various windows UxTheme
functions which are available since WinXP. As wxWidgets 3.1 is XP+ it
does not make sense anymore to load the theme functions dynamically.

include/wx/msw/libraries.h

@@ -22,4 +22,9 @@
 #pragma comment(lib, "oleacc")
 #endif
 
+#if defined __VISUALC__ && wxUSE_UXTHEME
+#pragma comment(lib, "uxtheme")
+#endif
+
+
 #endif /* _WX_MSW_LIBRARIES_H_ */