x11/xorg is a meta-port, which has no options of itself. The countless ports it draws in to build Xorg certainly have. You'll have to figure out which port it actually is ..
Some of them are:
Code:
/usr/ports/x11-drivers/xorg-drivers
/usr/ports/x11-fonts/xorg-fonts
/usr/ports/x11-servers/xorg-server
/usr/ports/x11-themes/xcursor-themes
/usr/ports/x11/xbitmaps
/usr/ports/x11/xorg-apps
/usr/ports/x11/xorg-docs
/usr/ports/x11/xorg-libraries
You can also check out the /var/db/ports/*/options files.