AIX has a macro "func_data" that conflicts with func_data variable

names in gtk.h.  This fix undef's the func_data macro before including
gtk.h.

src/sview/sview.h

@@ -55,6 +55,9 @@
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>
+#if defined(HAVE_AIX)
+#undef func_data
+#endif
 #include <gtk/gtk.h>
 
 #include "src/common/bitstring.h"