Fix Ubuntu 16 test VM, rename directory

Also remove the FreeBSD VM definition, as it basically does not work in
VirtualBox and Vagrant, for whatever reason.

vagrant/ubuntu16/Vagrantfile

@@ -0,0 +1,20 @@
+#
+# Vagrantfile for Ubuntu Linux 16.04 test environment.
+#
+Vagrant.configure(2) do |config|
+
+  config.vm.box = 'ubuntu/xenial64'
+
+  # need enough memory to build syntex_syntax crate
+  config.vm.provider 'virtualbox' do |vb|
+    vb.memory = 2048
+  end
+
+  # bring the system up to date
+  config.vm.provision 'shell', inline: <<-SHELL
+    sudo apt-get -y autoremove
+    sudo apt-get -y update
+    sudo apt-get -y upgrade
+  SHELL
+
+end