xorg-server: major bump 1.18.4 -> 1.19.1

I encountered no problems with it. Nvidia binary drivers are tested,
and AMD ones now both set `abiCompat` to use older server versions.

nixos/doc/manual/release-notes/rl-1703.xml

···
     xlink:href="https://nixos.org/nixpkgs/manual/#sec-overlays-install">Nixpkgs
     manual</link> for more information.</para>
   </listitem>
+
+  <listitem>
+    <para>X.org server uses branch 1.19.  Due to ABI incompatibilities,
+      <literal>ati_unfree</literal> keeps forcing 1.17
+      and <literal>amdgpu-pro</literal> starts forcing 1.18.</para>
+  </listitem>
 </itemizedlist>
 
 <para>The following new services were added since the last release:</para>

pkgs/servers/x11/xorg/default.nix

···
   }) // {inherit ;};
 
   xorgserver = (mkDerivation "xorgserver" {
-    name = "xorg-server-1.18.4";
+    name = "xorg-server-1.19.1";
     builder = ./builder.sh;
     src = fetchurl {
-      url = mirror://xorg/individual/xserver/xorg-server-1.18.4.tar.bz2;
-      sha256 = "1j1i3n5xy1wawhk95kxqdc54h34kg7xp4nnramba2q8xqfr5k117";
+      url = mirror://xorg/individual/xserver/xorg-server-1.19.1.tar.bz2;
+      sha256 = "1yx7cnlhl14hsdq5lg0740s4nxqxkmaav38x428llv1zkprjrbkr";
     };
-    buildInputs = [pkgconfig dri2proto dri3proto renderproto libdrm openssl libX11 libXau libXaw libxcb xcbutil xcbutilwm xcbutilimage xcbutilkeysyms xcbutilrenderutil libXdmcp libXfixes libxkbfile libXmu libXpm libXrender libXres libXt ];
+    buildInputs = [pkgconfig dri2proto dri3proto renderproto openssl libX11 libXau libXaw libxcb xcbutil xcbutilwm xcbutilimage xcbutilkeysyms xcbutilrenderutil libXdmcp libXfixes libxkbfile libXmu libXpm libXrender libXres libXt ];
     meta.platforms = stdenv.lib.platforms.unix;
-  }) // {inherit dri2proto dri3proto renderproto libdrm openssl libX11 libXau libXaw libxcb xcbutil xcbutilwm xcbutilimage xcbutilkeysyms xcbutilrenderutil libXdmcp libXfixes libxkbfile libXmu libXpm libXrender libXres libXt ;};
+  }) // {inherit dri2proto dri3proto renderproto openssl libX11 libXau libXaw libxcb xcbutil xcbutilwm xcbutilimage xcbutilkeysyms xcbutilrenderutil libXdmcp libXfixes libxkbfile libXmu libXpm libXrender libXres libXt ;};
 
   xorgsgmldoctools = (mkDerivation "xorgsgmldoctools" {
     name = "xorg-sgml-doctools-1.11";

pkgs/servers/x11/xorg/overrides.nix

···
         damageproto xcmiscproto  bigreqsproto
         inputproto xextproto randrproto renderproto presentproto
         dri2proto dri3proto kbproto xineramaproto resourceproto scrnsaverproto videoproto
+        libXfont2
       ];
       # fix_segfault: https://bugs.freedesktop.org/show_bug.cgi?id=91316
       commonPatches = [ ];

pkgs/servers/x11/xorg/tarballs-7.7.list

···
 mirror://xorg/individual/app/xmag-1.0.6.tar.bz2
 mirror://xorg/individual/app/xmodmap-1.0.9.tar.bz2
 mirror://xorg/individual/doc/xorg-docs-1.7.1.tar.bz2
-mirror://xorg/individual/xserver/xorg-server-1.18.4.tar.bz2
+mirror://xorg/individual/xserver/xorg-server-1.19.1.tar.bz2
 mirror://xorg/X11R7.7/src/everything/xorg-sgml-doctools-1.11.tar.bz2
 mirror://xorg/X11R7.7/src/everything/xpr-1.0.4.tar.bz2
 mirror://xorg/individual/app/xprop-1.2.2.tar.bz2