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

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>

Integration develop-nr 2020 week 03

See merge request oai/openairinterface5g!755

This integration branch includes the following MRs:

- MR 745 : Add support for different PUSCH DMRS modes
- MR 748 : Nr dlsch multi threading
- MR 752 : Merging develop tag 2019.w51 to develop-nr
- MR 753 : RedHat Entreprise 7.7 build support

IMPORTANT: This should be the last integration branch to develop-nr as the result of this MR will become develop

- New slot numbering approach was missing for PMCH case

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>

spare4 is not there in rrc 15.6. It leads to bad encoding.

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>

 - physical simulators
 - LTE eNB
 - LTE UE
 - 5G-NR gNB

Still NR-UE does not build and eNB segs fault at start of program
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>

Mainly comestics and integer type management
Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

Integration develop-nr 2020 week 02

See merge request oai/openairinterface5g!751

This integration branch contains the following MRs

* MR [706] : Merging develop tag `2019.w44` into develop-nr
* MR [746] : some cppcheck fixes and also compilation warnings removal
* MR [750] : hotfix: fix value of MAX_MOBILES_PER_ENB

Also contains an hotfix for the UHD thread priority