Develop integration 2020 week 04

See merge request oai/openairinterface5g!763

The following MRs have been included:

* MR [726] : Flexran improvements
* MR [756] : remove uhd_set_thread_priority function
* MR [757] : HOTFIX: After develop/develop-nr merge UE was crashing with MBMS U-Plane traffic running
* MR [758] : Improve build after nr lte merge
* MR [759] : Doc update after 5g lte merge and latest build procedure modifications
* MR [761] : fixes for mutex lock for wake up signal
* MR [761] : CI: count ULSCH received ok messages

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>

    split the RRC inactivity scenarios
Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

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

	-BUGFIX: CD/DU F1 split

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

update doc/BUILD.md and doc/RUNMODEM.md to reflect develop/develop-nr merge and latest merge requests affecting the build procedure

build improvements: allow build mode selection (-g -G options) allow all exec build in one pass, remove remaining USE_MME macros in nr code

The timer code used to trigger periodic statistics message sending used
ITTI. Together with a high frequency reporting (e.g. 1ms), this resulted
in high CPU usage. This commit reimplements this:
* using a thread that is synchronized to the RU (if there is no MAC, we
  assume there is no RU generating a tick so we create the tick source
  ourselves)
* no RB trees but plain arrays
* smaller interface for users
* slight user interface changes
* remove stopped timer state: such timer might be simply removed
* remove one-shot timers

* only set up timer for sending requests
* simplify interface for timer setup
* on timer expiry, do not pass through stats request function but
  directly send the reply
* Remove whatever report structure and use stats request directly for
  inferring the data to send

	-New MAC SDU integrity check in ue_procedures .c introduced for MCH channels.
	-This SDU behavior didn’t show up with former develop
	-TOCHECK whether NFAPI was properly merged on the eNB side.
	-eNB_scheduler_mch has been slightly rearranged.

	*BUGFIX:
	-In dlsch_demodulation.c  “ rxF_comp_d.m” was continuously being written to disk

	*New reference config file added (lte-fdd-mbms-basic-sim.conf) for rfsim environment

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