rfb: Avoid unused argument warnings in headers
Don't force users of these headers to squash compiler
warnings about unused arguments, annotate with __unused_attr.
diff --git a/common/rfb/util.h b/common/rfb/util.h
index e9114c3..0de64c4 100644
--- a/common/rfb/util.h
+++ b/common/rfb/util.h
@@ -38,6 +38,10 @@
# define __printf_attr(a, b)
#endif // __GNUC__
+#ifndef __unused_attr
+# define __unused_attr __attribute((__unused__))
+#endif
+
namespace rfb {
// -=- Class to handle cleanup of arrays of characters