NEW PORT sysutils/xen-tools

These tools are useful for debugging Xen related problems when one
does not have access to the dom0 or wants to view the entries from
domU's perspective. These work on FreeBSD VMs using the XEN (i386)
kernel or the XENHVM kernel.

Fix: Patch attached with submission follows:
How-To-Repeat: Example:

devwebbsd05# /usr/local/bin/xenstore-ls /local/domain/`/usr/local/bin/xenstore-read domid`

vm = "/vm/1a3ff05b-e843-6ebf-293f-b5a92c85ca5d"
vss = "/vss/1a3ff05b-e843-6ebf-293f-b5a92c85ca5d"
name = "CSN/XC/TEMPLATE/FREEBSD/8/2/DEVWEBBSD/VM/DEVWEBBSD05/125/185"
cpu = ""
 0 = ""
  availability = "online"
memory = ""
 initial-reservation = "1059840"
 static-max = "1048576"
 target = "1048576"
 dynamic-min = "1048576"
 dynamic-max = "1048576"
device = ""
 vbd = ""
  832 = ""
   backend = "/local/domain/0/backend/vbd/188/832"
   state = "4"
   backend-id = "0"
   device-type = "disk"
   virtual-device = "832"
   ring-ref = "768"
   ring-pages = "1"
   max-requests = "32"
   max-request-segments = "11"
   max-request-size = "40960"
   event-channel = "4"
   protocol = "x86_64-abi"
  5696 = ""
   backend = "/local/domain/0/backend/vbd/188/5696"
   state = "6"
   backend-id = "0"
   device-type = "cdrom"
   virtual-device = "5696"
   ring-ref = "769"
   ring-pages = "1"
   max-requests = "32"
   max-request-segments = "11"
   max-request-size = "40960"
   event-channel = "5"
   protocol = "x86_64-abi"
 vif = ""
  0 = ""
   backend = "/local/domain/0/backend/vif/188/0"
   backend-id = "0"
   state = "4"
   handle = "0"
   mac = "ce:af:53:8b:27:c8"
   tx-ring-ref = "770"
   rx-ring-ref = "771"
   event-channel = "6"
   request-rx-copy = "1"
   feature-rx-notify = "1"
   feature-sg = "1"
   feature-gso-tcpv4 = "1"
error = ""
drivers = ""
control = ""
 platform-feature-multiprocessor-suspend = "1"
attr = ""
data = ""
 set_clipboard = "https://admin.wayfair.com/tracker/views/89.php?PrtID=332389#"
messages = ""
platform = ""
 timeoffset = "-14821"
 nx = "false"
 acpi = "true"
 apic = "true"
 pae = "true"
 viridian = "true"
 vcpu = ""
  number = "1"
bios-strings = ""
 bios-vendor = "Xen"
 bios-version = ""
 system-manufacturer = "Xen"
 system-product-name = "HVM domU"
 system-version = ""
 system-serial-number = ""
 hp-rombios = ""
 oem-1 = "Xen"
 oem-2 = "MS_VM_CERT/SHA1/bdbeb6e0a816d43fa6d3fe8aaef04c2bad9d3e3d"
unique-domain-id = "9fd6261b-ae3d-355e-d4bb-34fdee660bf5"
domid = "188"
store = ""
 port = "2"
 ring-ref = "1044476"
qemu-pid = "21240"
device-misc = ""
 dm-ready = "1"
console = ""
 vnc-port = "5907"
 tty = "/dev/pts/50"
monitor = ""
 tty = "/dev/pts/13"
serial = ""
 0 = ""
  tty = "/dev/pts/50"