This commit introduces X2AP timers (t_reloc_prep, tx2_reloc_overall).
You need to set the values in the configuration file.

X2AP can be enabled or disabled in the configuration file too (disabled
by default).

Some deadcode was removed.

Some #if defined(ENABLE_USE_MME)/#endif were added here and there.
The nos1 softmodem has not been tested, maybe this commit breaks
things.

Some deadcode was removed.

The implementation of the ID management is not finished.
It will only work if the handover is successful. No error
recovery has been done. For error recovery, we need to
implement the X2AP timers. As it is, in case of error, an ID
might very well never be released.

It has been tested with 1 and 2 UEs doing handover more or less
at the same time.

- manage target eNB based on target cell id received by measurement report
  for Handover Request
- manage source eNB based on association id for Handover Request Ack
- use only x2ap instance and not x2ap data instance points to x2ap instance

- free correctly in rrc_eNB_free_mem_UE_context
- check for existence of ue_context.handover_info in rrc_enb_process_itti_msg
- check return value sctp_peeloff in sctp_handle_new_association_req_multi
  and exit in case of failure

When testing x2 handover, we found a race issue between the
RRC thread and the phy/mac thread (which is calling rrc_rx_tx).

The UE context was updated by the RRC thread but in the middle of
the update (which consists of several function calls and variables'
updates) the context was accessed by rrc_rx_tx. At this point, the
context was in an inconsistent state.

The solution is to access RRC data in the RRC thread only.
The function rrc_rx_tx now just sends an ITTI message to the
RRC thread. When receiving this message, the RRC thread does
the processing that was done by the function rrc_rx_tx (in
the new function rrc_subframe_process).

This way, the race condition disappears.

However we now send an ITTI message from the phy/mac thread to
the RRC thread at each subframe. That might increase the processing
time of the eNB. So maybe it's not the best solution. It may also
improve the realtime performance because less work is done by the
phy/mac realtime thread. To be checked somehow.

Also, it may be possible that some other RRC functions are still
called by the phy/mac thread, which should also be checked and
replaced by ITTI messages (if this solution is considered to be
correct).

With the introduction of X2AP into develop, the UEs now have to regularly
send measurement reports.

In the logs of the eNB, we see:

[OSA]   Mismatch found in integrity for algorithm 2,
        got e0.a0.c2.66, expecting a5.9c.cb.57
[PDCP]   [OSA][RB 1] eNB failed to validate MAC-I of incoming PDU

This is a bug in the PDCP layer that uses wrong parameters to compute the
integrity.

This commit fixes this bug.

The function pdcp_is_rx_seq_number_valid was removed. Its processing
has been directly integrated into the function pdcp_data_ind.

The function pdcp_mark_current_pdu_as_received is not called anymore.
Its processing was not used later on, so as of today, not calling it does
not introduce any functional change.

The function pdcp_validate_security takes now as parameters both
SN and HFN. Same for the function pdcp_get_next_count_rx.

Useless constants PDCP_SN_5BIT, PDCP_SN_7BIT and PDCP_SN_12BIT have been
removed.

The compilation option ENABLE_SECURITY has been removed. It's now always
on. (This may impact some use cases.)

The PDCP for DRB using RLC AM is not correct. It was not correct before
this commit (apart from the integrity bug). We should deal with a list
of PDUs and transmit packets to upper layers as detailed in the specs.
Today we transmit the PDU as soon as we get it. We don't care about
duplicates, in-order delivery, timeouts.

Also, we don't deal with "PDCP re-establishment". Not sure how that impacts
the software.

And, last but not least, there is still no ROHC.

Fix corrupted LOGs in L1L2simulator, introducing two new components NFAPI_VNF and NFAPI_pnf. Integrate Fujitsu fix for up to 50 UEs. Apply astyle to all modified files in the branch

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

This commits isolates the S1 UE Ctxt Rel Complete and GTP Tunnel Delete
Requests in functions and calls these function in the original place
(rrc_rx_tx()). The same functions are then used in the F1 UE Ctxt Rel
Complete handler to perform the same functionality, i.e. forward the UE
Ctxt Rel Complete message to the MME and free outstanding resources (RRC
context, GTP tunnels, S1 context).

remove L1L2 task, also remove some call to send messages to UNKNOWN_TASK, removed in new itti. Align LOG in rlc sources with new LOG code (remove DEBUG_RLC...)

When a phone loses connection, it should not simply be removed but first
CU should be informed which will send a ContextRelCmd. Correspondingly,
when the RRC releases the UE, it does not send a UE Context Release Req

For whatever reason most of the files had their permission
changed from 644 to 755, which is not wanted.