M1 progress: engine port compiles except pf.c; AF_DIVERT socket family; ifq framework

- compat layer extended through the full BSD API surface pf_ioctl/pf_lb/
  pf_if/pf_norm/pf_table/pf_ruleset/radix/md5/sha2 need (all compile):
  cpumem/counters model, ifaddr/ifg groups, cred view, endian+in6 names,
  NAT46/64, SipHash24, mbuf_list, frag6 helpers, ip6 forward/checksum,
  tcp options/FSM names, taskqueue & sysctl shims (documented in
  docs/porting-notes.md)
- pfsrc/divert_sock.c: real BSD divert(4) as runtime-registered PF_DIVERT=32
  socket family inside the module (sock_register; NPROTO=AF_MAX=45 -> zero
  core patches); divert_packet/divert6_packet wired for pf.c
- compat/pfk_ifq.c: OpenBSD 8.0 ifq framework with priq back end; hfsc and
  fq_codel aliases pending M5 (recorded in feature matrix as pending)
- design + plan updated for the divert decision (user-requested)
- stage-port.sh: single deterministic rename program for headers and .c

module/include/pfk_mbuf.h

@@ -15,6 +15,7 @@
 #include <linux/skbuff.h>
 
 struct pfk_ifnet;             /* forward (pfk_if.h) */
+struct mbuf_list;             /* BSD mbuf list (pfk_if.h defines it) */
 struct pf_state_key;
 struct inpcb;
 struct pf_tag;
@@ -61,7 +62,7 @@ struct pkthdr_pf {
 	u_int8_t		 dir;
 	u_int8_t		 reason;
 	u_int16_t		 ruleset;
-	struct pfk_tag		*tag;
+	u_int			 tag;	/* OpenBSD: bitmask */
 };
 
 struct pkthdr {
@@ -130,9 +131,9 @@ struct mbuf *m_dup(struct mbuf *m, int wait);	/* full dup + headroom */
 void  m_adj(struct mbuf *m, int dlen);
 void  m_trim(struct mbuf *m, int dlen);
 int   m_cat(struct mbuf *to, struct mbuf *from);	/* copies+consumes from */
-caddr_t m_copyback(struct mbuf *m, int off, int len, const void *copied);
+int m_copyback(struct mbuf *m, int off, int len, const void *copied, int type);
 void  m_copydata(const struct mbuf *m, int off, int len, caddr_t dest);
-caddr_t m_getptr(struct mbuf *m, int loc, int *off);
+struct mbuf *m_getptr(struct mbuf *m, int loc, int *off);
 int   m_clump(struct mbuf **m0p, int len, int *mp_off, int *mp_len, caddr_t *doff);
 void  m_free_ext(struct mbuf *m);
 struct mbuf *m_free(struct mbuf *m);		/* returns next */