Define ATTRIBUTE_PACKED and use as necessary.

include/ansidecl.h

@@ -361,6 +361,12 @@ So instead we use the macro below and test it against specific values.  */
 # endif /* GNUC >= 3.0 */
 #endif /* ATTRIBUTE_ALIGNED_ALIGNOF */
 
+/* Useful for structures whoes layout must much some binary specification
+   regardless of the alignment and padding qualities of the compiler.  */
+#ifndef ATTRIBUTE_PACKED
+# define ATTRIBUTE_PACKED __attribute__ ((packed))
+#endif
+
 /* We use __extension__ in some places to suppress -pedantic warnings
    about GCC extensions.  This feature didn't work properly before
    gcc 2.8.  */