X2AP: init funcs (register/association) + handler/management functions

SCTP: one to many sockets implementation

targets/COMMON/create_tasks.c

@@ -27,6 +27,7 @@
 # ifdef OPENAIR2
 #   if defined(ENABLE_USE_MME)
 #     include "sctp_eNB_task.h"
+#     include "x2ap_eNB.h"
 #     include "s1ap_eNB.h"
 #     include "nas_ue_task.h"
 #     include "udp_eNB_task.h"
@@ -62,6 +63,11 @@ int create_tasks(uint32_t enb_nb)
 
 #   if defined(ENABLE_USE_MME)
       if (enb_nb > 0) {
+        if (itti_create_task (TASK_X2AP, x2ap_task, NULL) < 0) {
+          LOG_E(X2AP, "Create task for X2AP failed\n");
+          return -1;
+        }
+
         if (itti_create_task (TASK_SCTP, sctp_eNB_task, NULL) < 0) {
           LOG_E(SCTP, "Create task for SCTP failed\n");
           return -1;