Fix the "rake test" target.

It was failing because the different os-specific files redefine the same
symbols.  Therefore, they can't all be required in the same process.  I
split them up into three processes.  Also, :test was redundant with
:test_units, so I removed the latter.
s/Fauled/Failed
Fix dragonflybsd's test_interface_list.

The list wasn't sorted.  This should've been applied in change
6b2b2e8b7554b14221388971516095d0933acc2a, but wasn't due to an
oversight.
Added a test_mtu test for FreeBSD.

No existing test checked the parsing of freebsd_netstat.txt.  I had to
add it to the test file.  I also had to make up example data for rl0.
It seems that the author created freebsd.txt and freebsd_netstat.txt at
different times or with different configurations.
Fix formatting error from change 9d7ed132f5eb61258d38fc2b8b68457f63dd460c
Fix Rx/Tx statistics on FreeBSD

In r199803 on 2009-11-25, FreeBSD added an "Idrop" column to netstat(1).
All currently supported releases of FreeBSD include that column.

ifconfig_examples/freebsd_netstat.txt
	Add an Idrop column.  Remove the "Drop" column, which would only
	be present with "-d".  Remove the "Ibytes" and "Obytes" columns,
	which would only be present with "-b".

lib/ifconfig/bsd/ifconfig.rb
	Parse netstat(1)'s output's header instead of assuming fixed
	positions for fields.

test/unit/tc_freebsd.rb
	Add asserts for the rx and tx packets and errors.
Update the FreeBSD example files with output from FreeBSD 9.2.

The new files don't include aliases or any IPv6 address other than
link-local, but they do include fibs and laggs.  Also, the old file
appears to have been created without the "-n" option.
Add support for FreeBSD fibs.
Never invoke IO::popen during unit tests.

Previously, the unit tests were all invoking "netstat -in" because its
output wasn't injected.  I fixed this by injecting it in all tests.  I
also had to change some function signatures.

test/unit/tc_netbsd.rb
ifconfig_examples/netbsd_netstat.txt
	Create netbsd netstat output based on the behavior of NetBSD
	6.0 amd64

ifconfig_examples/sunos_netstat.txt
test/unit/tc_sunos.rb
	Create sunos netstat output based on the behavior of Illumian
	1.0 (a5) i386.

test/unit/tc_dragonflybsd.rb
	Use the existing netstat output for dragonfly bsd

test/unit/tc_darwin.rb
test/unit/tc_openbsd.rb
test/unit/tc_osx.rb
	Use the empty string as netstat output because I don't have
	access to these platforms.  The existing testcases don't
	actually check the results of parsing netstat anyway.

lib/ifconfig/bsd/interface_types.rb
lib/ifconfig/common/interface_types.rb
lib/ifconfig/linux/interface_types.rb
lib/ifconfig/sunos/ifconfig.rb
lib/ifconfig/sunos/interface_types.rb
	Add a "netstattxt" parameter to parse_ifconfig to allow
	netstat's output to be injected on sunos.
Added media type detection for BSD.

ifconfig_examples/freebsd.txt
ifconfig_examples/freebsd_netstat.txt
test/unit/tc_freebsd.rb
	Added a 10G interface to the examples for FreeBSD

lib/ifconfig/bsd/interface_types.rb
lib/ifconfig/common/interface_types.rb
	Added parse_media.  It's a noop for non-BSD.
Added specific support for link aggregation

lib/ifconfig/bsd/ifconfig.rb
lib/ifconfig/bsd/interface_types.rb
lib/ifconfig/common/interface_types.rb
	Added a LinkAggregation interface type.  It only works on
	FreeBSD ATM.

test/unit/tc_freebsd.rb
	Added tests for the existing example output files.