Document AllowOverride parameter.

unix/xserver/hw/vnc/Xvnc.man

@@ -300,6 +300,21 @@ Key affected by NumLock often require a fake Shift to be inserted in order
 for the correct symbol to be generated. Turning on this option avoids these
 extra fake Shift events but may result in a slightly different symbol
 (e.g. a Return instead of a keypad Enter).
+.
+.TP
+.B \-AllowOverride
+Comma separated list of parameters that can be modified using VNC extension.
+Parameters can be modified for example using \fBvncconfig\fP(1) program from
+inside a running session.
+
+Allowing override of parameters such as \fBPAMService\fP or \fBPasswordFile\fP
+can negatively impact security if Xvnc runs under different user than the
+programs allowed to override the parameters.
+
+When \fBNoClipboard\fP parameter is set, allowing override of \fBSendCutText\fP
+and \fBAcceptCutText\fP has no effect.
+
+Default is \fBdesktop,AcceptPointerEvents,SendCutText,AcceptCutText\fP.
 
 .SH USAGE WITH INETD
 By configuring the \fBinetd\fP(1) service appropriately, Xvnc can be launched