Rename SESMAN_CFG_X11DISPLAYOFFSET to SESMAN_CFG_SESS_X11DISPLAYOFFSET

Move it to other session options in config.h. X11DisplayOffset is part of
the [Sessions] section.

sesman/config.c

@@ -347,7 +347,7 @@ config_read_sessions(int file, struct config_sessions *se, struct list *param_n,
     {
         buf = (char *)list_get_item(param_n, i);
 
-        if (0 == g_strcasecmp(buf, SESMAN_CFG_X11DISPLAYOFFSET))
+        if (0 == g_strcasecmp(buf, SESMAN_CFG_SESS_X11DISPLAYOFFSET))
         {
             se->x11_display_offset = g_atoi((char *)list_get_item(param_v, i));
         }

sesman/config.h

@@ -37,7 +37,6 @@
 #define SESMAN_CFG_PORT              "ListenPort"
 #define SESMAN_CFG_ENABLE_USERWM     "EnableUserWindowManager"
 #define SESMAN_CFG_USERWM            "UserWindowManager"
-#define SESMAN_CFG_X11DISPLAYOFFSET  "X11DisplayOffset"
 #define SESMAN_CFG_MAX_SESSION       "MaxSessions"
 #define SESMAN_CFG_AUTH_FILE_PATH    "AuthFilePath"
 
@@ -66,6 +65,7 @@
 #define SESMAN_CFG_SESS_KILL_DISC    "KillDisconnected"
 #define SESMAN_CFG_SESS_IDLE_LIMIT   "IdleTimeLimit"
 #define SESMAN_CFG_SESS_DISC_LIMIT   "DisconnectedTimeLimit"
+#define SESMAN_CFG_SESS_X11DISPLAYOFFSET "X11DisplayOffset"
 
 #define SESMAN_CFG_SESS_POLICY_S "Policy"
 #define SESMAN_CFG_SESS_POLICY_DFLT_S "Default"