The sysctl uptime fixture was little endian, which fails on sparc
hardware. Added a big endian fixture and endian detection.

Due to "netstat -rn" returning multiple protocols (IPv4 and IPv6) the
"default_interface" can get more than one entry in to it, causing the
macaddress resolving to break. This limits it to just one interface.

This stubs out the platform side of the code, and uses fixtures emitting the
right output from the interface configuration tools.

Paired-With: Matt Robinson <matt@puppetlabs.com>
Paired-With: Max Martin <max@puppetlabs.com>

'who -b' doesn't report the year of the last system boot on (at least)
Solaris 10, and OpenSolaris 2009.06.  Try using 'kstat -p
unix:::boot_time', which reports as seconds since the epoch on these
systems before falling back to 'who -b'.

Reviewed-by: Paul Berry <paul@puppetlabs.com>

Regexp tested the s_context or VxID field if /proc/self/status and
returned false for 0 and true for any other number. 0 indicates a host,
which is still virtual.

Fix changes regexp to correctly report hosts as virtual. Tested against
vserver 2.1 and 2.3.

* With tests for 9.8.0, 10.3.0 and 10.6.4

Rewrite of uptime facts and supporting utility methods. Works on unix,
BSD, windows. No longer makes redundant system calls.

Uses Facter::Util::Uptime utility methods:

* Implemented uptime_seconds_unix using /proc/uptime or who -b on unix,
  sysctl on BSD.

  Added unit tests for the behaviors of get_uptime_seconds_unix: read
  from proc/uptime, read uptime from "sysctl -b kern.boottime", read
  uptime from "who -b", and return nil if nothing else works.

* Implemented uptime_seconds_win using the Win32 API.

Facts implemented:

* uptime_{seconds,hours,days}

    Returns the respective integer value.

* uptime

    Returns human readable uptime statistic that preserves original
    behavior.

    Examples:

      3 days
      1 day
      5:08 hours
      0:35 hours