doc: xrdp-dis manual page

Add a manual page for xrdp-dis, which is used to disconnect the RDP
connection but otherwise keep the session running.

docs/man/Makefile.am

@@ -1,4 +1,5 @@
 man_MANS = \
+  xrdp-dis.1 \
   sesman.ini.5 \
   xrdp.ini.5 \
   xrdp.8 \

docs/man/xrdp-dis.1

@@ -0,0 +1,23 @@
+.TH "xrdp-dis" "8" "0.7.0" "xrdp team"
+.SH NAME
+xrdp\-dis \- xrdp disconnect utility
+
+.SH SYNOPSIS
+.B xrdp\-dis
+
+.SH DESCRIPTION
+.PP
+\fBxrdp\-dix\fP is run with no parameters to disconnect your xrdp session.
+
+.SH ENVIRONMENT
+.TP
+.B DISPLAY
+to get the default host and display number.
+
+.SH FILES
+.TP
+.I /tmp/.xrdp/xrdp_disconnect_display_*
+UNIX socket used to communicate with the \fBxrdp\fP(8) session manager.
+
+.SH SEE ALSO
+.BR xrdp (1).