Work around the use of "register" in DirectDB headers

This keyword results in deprecation warnings since C++11 and errors
since C++17 in which it was completely removed.

include/wx/dfb/wrapdfb.h

@@ -14,9 +14,14 @@
 #include "wx/gdicmn.h"
 #include "wx/vidmode.h"
 
+// "register" is removed in C++17 but used inside these headers.
+#define register
+
 #include <directfb.h>
 #include <directfb_version.h>
 
+#undef register
+
 // DFB < 1.0 didn't have u8 type, only __u8
 #if DIRECTFB_MAJOR_VERSION == 0
 typedef __u8 u8;