nvidia nouveau Xorg no display workaround

In Xorg newer than t9, Xorg stopped automatically loading the nouveau module, which causes no hdmi output on my GTX 670 card, except in virtual terminals. I tracked it down by by comparing Xorg logs.

Based on https://nouveau.freedesktop.org/InstallNouveau.html , I fixed it with

mkdir -p /etc/X11/xorg.conf.d
cat >/etc/X11/xorg.conf.d/20-nouveau.conf <<'EOF'
Section "Device"
Identifier "Device0"
Driver "nouveau"
EndSection
EOF

Then restarting Xorg.

I plan to look into fixing this regression and getting it backported to trisquel 10.

Its failing as early as xserver-xorg-core 1.20.1-3ubuntu2 (not sure exactly which of the many xorg package's fault it is).