Remove the --sync commandline option

Remove the --sync option and remove the possibility of backend-specific
commandline options altogether. --sync is being replaced by
a GDK_SYNCHRONIZE environment variable.

docs/reference/gtk/running.sgml

@@ -368,6 +368,15 @@ nevertheless.
   </para>
 </formalpara>
 
+<formalpara>
+  <title><envar>GDK_SYNCHRONIZE</envar></title>
+
+  <para>
+    If set, GDK makes all X requests synchronously. This is a useful
+    option for debugging, but it will slow down the performance considerably.
+  </para>
+</formalpara>
+
 <formalpara>
   <title><envar>XDG_DATA_HOME</envar>, <envar>XDG_DATA_DIRS</envar></title>
 

docs/reference/gtk/x11.sgml

@@ -20,13 +20,13 @@ X11 aspects of using GTK+
 <title>GTK+ for the X Window System</title>
 
 <para>
-On UNIX, the X backend is the default build for GTK+. So 
-you don't need to do anything special when compiling it,
+On UNIX, the X backend is the default build for GTK+.
+So you don't need to do anything special when compiling it,
 and everything should "just work."
 </para>
 
 <para>
-To mix low-level Xlib routines into a GTK program, 
+To mix low-level Xlib routines into a GTK program,
 see <link linkend="gdk-X-Window-System-Interaction">GDK X Window
 System interaction</link> in the GDK manual.
 </para>
@@ -35,8 +35,7 @@ System interaction</link> in the GDK manual.
 <title>X11-specific commandline options</title>
 
 <para>
-The X backend understands some additional command line 
-arguments.
+The X backend understands some additional command line arguments.
 </para>
 
 <formalpara>
@@ -48,15 +47,6 @@ in the <envar>DISPLAY</envar> environment variable.
 </para>
 </formalpara>
 
-<formalpara>
-<title><systemitem>--sync</systemitem></title>
-
-<para>
-Makes all X requests synchronously. This is a useful option for
-debugging, but it will slow down the performance considerably.
-</para>
-</formalpara>
-
 </refsect2>
 
 </refsect1>