Introduce instance_name field into xrdp.ini and xrdp-sesrun, along with

the N policy in sesman.ini, allowing xrdp sessions to be tagged with an
instance name to enable persistent association with a specific
xrdp instance, to allow experiences where users reconnect to specific
sessions based on e.g. the xrdp listening port used.

sesman/ercp_process.c

@@ -43,6 +43,7 @@ process_session_announce_event(struct session_item *si)
 {
     int rv;
     const char *start_ip_addr;
+    const char *instance_name;
     unsigned int display;
 
     rv = ercp_get_session_announce_event(si->sesexec_trans,
@@ -54,7 +55,8 @@ process_session_announce_event(struct session_item *si)
                                          &si->bpp,
                                          &si->guid,
                                          &start_ip_addr,
-                                         &si->start_time);
+                                         &si->start_time,
+                                         &instance_name);
     if (rv == 0)
     {
         // We may already know the display we sent sesexec. If we do,
@@ -71,6 +73,8 @@ process_session_announce_event(struct session_item *si)
     {
         snprintf(si->start_ip_addr, sizeof(si->start_ip_addr),
                  "%s", start_ip_addr);
+        snprintf(si->xrdp_instance_name, sizeof(si->xrdp_instance_name),
+                 "%s", instance_name);
         si->display = display;
 
         si->state = E_SESSION_RUNNING;