Upstream removed this configure option back in 2010 (for server 1.8):
http://cgit.freedesktop.org/xorg/xserver/commit/?id=60b6477f6dc005a1b052be8c5
So this hasn't done anything since 759d548e3e (xserver_xorg-server: bump
version).
Don't add any Config.in.legacy for this as it as been broken for so long any
way.
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>