this is for fixing the unaligned kernel memory access and 
mcopy_m sanity when the tcp selective acknoledgement is enabled.


panic form 40F bl22

stack trace of unaligned kernel memory access in kernel mode.

> 0 stop_secondary_cpu src/kernel/arch/alpha/cpu.c : 614
 1 panic src/kernel/bsd/subr_prf.c : 751
 2 event_timeout src/kernel/arch/alpha/cpu.c : 1183
 3 xcpu_puts src/kernel/bsd/subr_prf.c : 895
 4 printf src/kernel/bsd/subr_prf.c : 423
 5 panic src/kernel/bsd/subr_prf.c : 804
 6 afault_trap src/kernel/arch/alpha/trap.c : 2594
 7 _XentUna src/kernel/arch/alpha/locore.s : 1863
 8 tcp_dooptions src/kernel/netinet/tcp_input.c : 2391
 9 tcp_input src/kernel/netinet/tcp_input.c : 1153
 10 ipintr src/kernel/netinet/ip_input.c : 1225
 11 netisr_thread src/kernel/net/netisr.c : 1278 


stack trace for m_copym sanity

>  0 boot                 src/kernel/arch/alpha/machdep.c : 2038
   1 panic                src/kernel/bsd/subr_prf.c : 755
   2 event_timeout        src/kernel/arch/alpha/cpu.c : 1183
   3 pmap_update_send     src/kernel/arch/alpha/pmap_update.c : 257
   4 pmap_tbsync          src/kernel/arch/alpha/pmap.c : 4660
   5 pmap_copy_on_write   src/kernel/arch/alpha/pmap.c : 4013
   6 pmap_page_protect    src/kernel/arch/alpha/pmap.c : 4059
   7 ubc_flush_dirty_age  src/kernel/vfs/vfs_ubc.c : 3555
   8 ubc_flush_dirty      src/kernel/vfs/vfs_ubc.c : 3402
   9 mntflushbuf          src/kernel/vfs/vfs_bio.c : 1672
  10 boot                 src/kernel/arch/alpha/machdep.c : 1967
  11 panic                src/kernel/bsd/subr_prf.c : 842
  12 m_copym              src/kernel/bsd/uipc_mbuf.c : 705
  13 tcp_output           src/kernel/netinet/tcp_output.c : 621
  14 tcp_input            src/kernel/netinet/tcp_input.c : 2163
  15 ipintr               src/kernel/netinet/ip_input.c : 1225
  16 netisr_thread        src/kernel/net/netisr.c : 1278

