pflog alignment fix

[Henning Brauer]

so just pad the header to be a mutiple of 8 bytes, makes pflogd happy
on 64bit archs

Index: if_pflog.h
===================================================================
RCS file: /cvs/src/sys/net/if_pflog.h,v
retrieving revision 1.17
diff -u -p -r1.17 if_pflog.h
--- if_pflog.h  21 Sep 2010 11:05:10 -0000      1.17
+++ if_pflog.h  17 Oct 2010 22:02:47 -0000
@@ -59,6 +59,7 @@ struct pfloghdr {
        struct pf_addr  daddr;
        u_int16_t       sport;
        u_int16_t       dport;
+       u_int8_t        pad2[4];
 };
 
 #define PFLOG_HDRLEN           sizeof(struct pfloghdr)