Attempt to improve application portability by marking `struct ar_hdr'

as `packed'.

The C standard leaves the alignment of individual members of a C
struct upto the implementation, so pedantically speaking portable
code cannot assume that the layout of a `struct ar_hdr' in memory
will match its layout in a file.  Using a __packed attribute
declaration forces file and memory layouts for this structure to
match.

Submitted by:	ru

include/ar.h

@@ -39,11 +39,15 @@
  * SUCH DAMAGE.
  *
  *	@(#)ar.h	8.2 (Berkeley) 1/21/94
+ *
+ * $FreeBSD$
  */
 
 #ifndef _AR_H_
 #define	_AR_H_
 
+#include <sys/cdefs.h>
+
 /* Pre-4BSD archives had these magic numbers in them. */
 #define	OARMAG1	0177555
 #define	OARMAG2	0177545
@@ -62,6 +66,6 @@ struct ar_hdr {
 	char ar_size[10];		/* size in bytes */
 #define	ARFMAG	"`\n"
 	char ar_fmag[2];		/* consistency check */
-};
+} __packed;
 
 #endif /* !_AR_H_ */