Document xserverbpp, add it to Xvnc section, remove from Xorg section

xserverbpp affects X11rdp and Xvnc, but not Xorg. No need to have
xserverbpp in the Xorg section where it has no effect. Add commented out
xserverbpp to Xvnc, some users may want to experiment with that setting.

docs/man/xrdp.ini.5

@@ -287,6 +287,12 @@ Specifies the ip address of the host to connect to.
 \fBport\fR=\fI<number>\fR|\fI\-1\fR
 Specifies the port number to connect to. If set to \fI\-1\fR, the default port for the specified library is used.
 
+.TP
+\fBxserverbpp\fR=\fI<number>\fR
+Specifies color depth of the backend X server. The default is the color
+depth of the client. Only Xvnc and X11rdp use that setting. Xorg runs at
+\fI24\fR bpp.
+
 .TP
 \fBcode\fR=\fI<number>\fR|\fI\-1\fR
 Specifies the session type, the default, \fI\0\fR, is Xvnc, \fI\10\fR, is X11rdp, and \fI\20\fR, uses Xorg driver mode.

xrdp/xrdp.ini

@@ -162,7 +162,6 @@ username=ask
 password=ask
 ip=127.0.0.1
 port=-1
-xserverbpp=24
 code=20
 
 [Xvnc]
@@ -172,6 +171,7 @@ username=ask
 password=ask
 ip=127.0.0.1
 port=-1
+#xserverbpp=24
 #delay_ms=2000
 
 [console]