nano -w /etc/portage/package.mask/xorg-7.1

# Mask xorg-x11-7.1
>=virtual/x11-7.1
>=x11-base/xorg-x11-7.1
>=x11-base/xorg-server-1.1.0
>=app-doc/xorg-docs-1.2
>=x11-drivers/xf86-input-evdev-1.1.2-r1
>=x11-drivers/xf86-video-vesa-1.2.0
>=x11-drivers/xf86-input-mouse-1.1.1
>=x11-drivers/xf86-input-keyboard-1.1.0
>=x11-drivers/xf86-video-ati-6.6.0
>=x11-drivers/xf86-video-nv-1.1.2
>=x11-drivers/xf86-video-v4l-0.1.1