xfree86: Document how -configdir affects the xorg.conf.d search path

Explain the "safe" path dance for -configdir, too.
Signed-off-by: Dan Nicholson <dbn.lists@gmail.com>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

hw/xfree86/doc/man/xorg.conf.man.pre

@@ -102,10 +102,12 @@ is the machine's hostname as reported by
 .BR gethostname (__libmansuffix__).
 .PP
 Additional configuration files are searched for in the following
-directories:
+directories when the server is started as a normal user:
 .PP
 .RS 4
 .nf
+.IR /etc/X11/ <cmdline>
+.IR __projectroot__/etc/X11/ <cmdline>
 .I /etc/X11/__xconfigdir__\-4
 .I /etc/X11/__xconfigdir__
 .I /etc/__xconfigdir__
@@ -118,6 +120,38 @@ directories:
 .fi
 .RE
 .PP
+where
+.I <cmdline>
+is a relative path (with no \(lq..\(rq components) specified with the
+.B \-configdir
+command line option.
+.PP
+When the __xservername__ server is started by the \(lqroot\(rq user, the
+config directory search locations are as follows:
+.PP
+.RS 4
+.nf
+<cmdline>
+.IR /etc/X11/ <cmdline>
+.IR __projectroot__/etc/X11/ <cmdline>
+.I /etc/X11/__xconfigdir__\-4
+.I /etc/X11/__xconfigdir__
+.I /etc/__xconfigdir__
+.IR __projectroot__/etc/X11/__xconfigdir__. <hostname>
+.I __projectroot__/etc/X11/__xconfigdir__\-4
+.I __projectroot__/etc/X11/__xconfigdir__
+.IR __projectroot__/lib/X11/__xconfigdir__. <hostname>
+.I __projectroot__/lib/X11/__xconfigdir__\-4
+.I __projectroot__/lib/X11/__xconfigdir__
+.fi
+.RE
+.PP
+where
+.I <cmdline>
+is the path specified with the
+.B \-configdir
+command line option (which may be absolute or relative).
+.PP
 The
 .I __xconfigfile__
 and