change the type of the opcode from enum *:8 to u_int8_t

so the size and alignment of the ipfw_insn is not compiler dependent.
No changes in the code generated by gcc.

There was only one instance of this kind in our entire source tree,
so i suspect the old definition was a poor choice (which i made).

MFC after:	3 days

sys/netinet/ip_fw.h

@@ -237,7 +237,7 @@ enum ipfw_opcodes {		/* arguments (4 byte each)	*/
  *
  */
 typedef struct	_ipfw_insn {	/* template for instructions */
-	enum ipfw_opcodes	opcode:8;
+	u_int8_t 	opcode;
 	u_int8_t	len;	/* number of 32-bit words */
 #define	F_NOT		0x80
 #define	F_OR		0x40