Sync cpu_reboot with i386:
- avoid sync and unmount after panic.
- remove vfs_shutdown, we call vfs_sync_all and vfs_unmount* instead.
- resurrect doshutdownhooks since some drivers still use it (eg. sab(4)).
Fix invalid free in deletextattr FUSE handler

Do not free FUSE message on error as it was not allocated.
Work around the problem in PR port-amd64/49150 for all CPUs under Xen.

The problem (calling xrstor, which is privileged in Xen) has appeared
on some Intel CPUs as well, so implement the workaround (ensure that
x86_xsave_features is 0) for all CPUs, not just AMD CPUs.

XXX pullup to 7
Correct 32 and 64 bit byte swap inlines.
Shave an instruction from the generated code for the 32 bit byte
swap inline.  Prune 5 or 9 instructions (depending on what you count)
from the 64 bit byte swap inline.
Mark sshbuf_putfv as __printflike.
sighup_handler is not dead.
xor32 may be unused, mark it so.
Import openresolv-3.6.1 with the following changes:
  *  Don't update when nothing has been deleted
  *  Backup resolv.conf to resolv.conf.bak when it doesn't have an openresolv
     signature
     Restore it when the new resolv.conf only has the openresolv signature
  *  Document prepend_search and prepend_nameservers
  *  Implement append_search and append_nameservers
  *  Implement replace and replace_sub to allow for keyword/value/replacement
Sync
Don't install rumpuser.h here.

It's already installed by the rump kernel build (sys/rump/include/rump)
actually support EMP
( as in, look for additional motion info bits, not just buttons )
Sync
simplify and correct.
Note import of dhcpcd and openresolv.
Correct 32 and 64 bit byte swap inlines
Add Realtek RTL8402 PCI-E Card Reader.
regen
Don't hang when booting Cubietruck via FEL.
Mark comintr as MP safe; otherwise a MULTIPROCESSOR kernel will try to
take the kernel_lock which breaks the locking protocol (should only be
taken at IPL_VM)