Upgrade doc/test VM to Ubuntu 16.04.

* This will help catch Perl errors in the doc code since it is not run across multiple OSs like the core and test code.
* It is to be hoped that a newer kernel will make Docker more stable.

.gitignore

@@ -3,6 +3,7 @@
 *.swp
 test/test
 test/.vagrant
+test/package
 test/nytprof.out
 test/nytprof/*
 doc/output/*

test/Vagrantfile

@@ -4,7 +4,7 @@ Vagrant.configure(2) do |config|
         vb.cpus = 8
     end
 
-    config.vm.box = "boxcutter/ubuntu1404-docker"
+    config.vm.box = "boxcutter/ubuntu1604"
 
     config.vm.provider :virtualbox do |vb|
         vb.name = "backrest-test"
@@ -12,11 +12,21 @@ Vagrant.configure(2) do |config|
 
     # Provision the VM
     config.vm.provision "shell", inline: <<-SHELL
-        # Install Perl modules
-        sudo apt-get update
-        apt-get install -y libdbi-perl libdbd-pg-perl libxml-checker-perl ghostscript libperl-critic-perl vim
+        # Install Docker
+        apt-get update
+        apt-get install -y apt-transport-https ca-certificates
+        apt-key adv --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D
+        echo 'deb https://apt.dockerproject.org/repo ubuntu-xenial main' > /etc/apt/sources.list.d/docker.list
+        apt-get update
+        apt-get install -y linux-image-extra-$(uname -r)
+        apt-get install -y docker-engine
+        service docker start
+        sudo usermod -aG docker vagrant
 
-        # Install texlive
+        # Install Perl modules
+        apt-get install -y libdbd-pg-perl libxml-checker-perl ghostscript libperl-critic-perl vim
+
+        # Install Texlive
         mkdir /root/texlive
         wget -q -O - http://mirror.hmc.edu/ctan/systems/texlive/tlnet/install-tl-unx.tar.gz \
             | tar zxv -C /root//texlive --strip-components=1
@@ -30,8 +40,8 @@ Vagrant.configure(2) do |config|
         /usr/local/texlive/2015/bin/x86_64-linux/tlmgr install caption xcolor listings parskip helvetic ltablex titlesec \
             epstopdf courier sectsty pgf ms
 
-        # Build vm images
-        /backrest/test/test.pl --vm-build
+        # Build VM images
+        sudo -u vagrant /backrest/test/test.pl --vm-build
     SHELL
 
   # Don't share the default vagrant folder