merge xorg-server 1.20.3.

CVE-2017-10971 and CVE-2017-10972: apply fixes to the event loop from

https://cgit.freedesktop.org/xorg/xserver/commit/?id=ba336b24052122b136486961c82deac76bbde455
https://cgit.freedesktop.org/xorg/xserver/commit/?id=8caed4df36b1f802b4992edcfd282cbeeec35d9d
https://cgit.freedesktop.org/xorg/xserver/commit/?id=215f894965df5fb0bb45b107d84524e700d2073c
https://cgit.freedesktop.org/xorg/xserver/commit/?id=05442de962d3dc624f79fc1a00eca3ffc5489ced

XXX: pullup-[678] (6/7 also need xfree port.)

initial import of xorg-server-1.18.4

import xorg-server 1.9.2. important changes since 1.6.5 include:

- built-in symbol visibility, default not export
- fixes for various crashes
- many fixes for XI2, EXA, dix, render, glx, xkb, EDID, randr, Xv,
resource handling, Xext, vfb, xfree86 / vga and composite support.
- fixes several memory leaks
- many many documentation updates
- record extension enabled
- no longer looks for XF86Config files

initial import of xorg-server-1.4.2