configuration files for CU/DU (thread policy)

also:
removed XFORMS from lte-softmodem target and associated extra functions in lte-softmodem.c
Conflicts:
	common/utils/T/T_defs.h
	targets/RT/USER/lte-softmodem.c

The following Merge Requests are included:

* MR 557 : Implement CDRX in FDD mode
* MR 571 : Improvement on documentation
* MR 572 : Fix CU/DU protocol split
* MR 574 : Fix a flexran free issue
* MR 578 : CI -- Improve OAI UE testing with USRP

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

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

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

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

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

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

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

changed CI configuration files so that the scheduling paramter for TDD and TM2 is "PARALLEL_SINGLE_THREAD"

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

 --> looping during the initOAIUE stage

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

Conflicts:
	openair1/PHY/defs_eNB.h
	openair1/SCHED/fapi_l1.c
	openair1/SCHED/phy_procedures_lte_eNb.c
	openair1/SCHED/prach_procedures.c
	openair2/LAYER2/MAC/eNB_scheduler.c
	openair2/LAYER2/MAC/eNB_scheduler_RA.c
	openair2/LAYER2/MAC/eNB_scheduler_primitives.c
	targets/RT/USER/lte-enb.c
	targets/RT/USER/lte-ru.c
	targets/RT/USER/lte-softmodem.c
	targets/RT/USER/lte-uesoftmodem.c

* Instead of partly initializing in read_config_and_init(), everything of
  PDCP is initialized in main() of lte-softmodem
* Omit RC.rrc access in RRU through checking of RC.nb_inst > 0
* Includes FlexRAN, i.e. do not start FlexRAN in RRU
* Function pointers to PDCP functions have to be set explicitly (avoid
  confusion of multiply setting function pointers)

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

changes in PARALLEL_RU_L!_TRX_SPLIT configuration. Correction of a few bugs related to passing of variables between threads

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

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

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

Merge branch '421-cdrx-for-lte' of https://gitlab.eurecom.fr/oai/openairinterface5g into 421-cdrx-for-lte