Implement native wxAuiTabArt for MSW

This wxAuiTabArt implementation uses Windows uxtheme API to draw AUI tabs. A
fallback to generic tab art is implemented for the bottom tabs or if uxtheme
is not available (disabled by user or no manifest file).

Closes https://github.com/wxWidgets/wxWidgets/pull/105

include/wx/aui/tabart.h

@@ -312,6 +312,10 @@ protected:
         #define wxHAS_NATIVE_TABART
         #include "wx/aui/tabartgtk.h"
         #define wxAuiDefaultTabArt wxAuiGtkTabArt
+    #elif defined(__WXMSW__)
+        #define wxHAS_NATIVE_TABART
+        #include "wx/aui/tabartmsw.h"
+        #define wxAuiDefaultTabArt wxAuiMSWTabArt
     #endif
 #endif // !__WXUNIVERSAL__