Merge branch 'nr_initialsync' of https://gitlab.eurecom.fr/oai/openairinterface5g into nr_initialsync

Merge branch 'nr_initialsync' of https://gitlab.eurecom.fr/oai/openairinterface5g into nr_initialsync

Merge branch 'nr_initialsync' of https://gitlab.eurecom.fr/oai/openairinterface5g into nr_initialsync

Conflicts:
	cmake_targets/build_oai
	openair1/PHY/LTE_TRANSPORT/prach.c
	openair1/SCHED/phy_procedures_lte_ue.c
	targets/ARCH/COMMON/common_lib.h
	targets/RT/USER/lte-softmodem.c

Summary of changes:
- bug fix in the FlexRAN API (correct a check)
- bug fix for sending the right RNTI in a FlexRAN message
- fixes small bug in ulsim which kills one RX antenna in channel simulation.
  Another simple but bad bug in ulsch_demodulation.c (bad access of avgU
  array). This probably resulted in a performance degradation for non-ideal
  channels, even for 1 antenna. The avgU was read in position 1 instead of
  0 for 1-antenna and in positions 1 and 2 instead of 0 and 1 for 2-antennas.
- work from Nokia:
    1) shared library loader, with integration for oai devices, encoder and telnet server
    2) telnet server (use build-oai --build-telnetsrv option and --telnetsrv softmodem option)
    3) UE/eNB in different executables (lte-uesoftmodem and lte-softmodem + noS1 variants)
    4) config module fixes and extensions
    5) very preliminary NB-IoT integration preparation, using shared lib loader ( use make NB-IoT to build, after building the eNB softmodem)
    6) Rename NB-IoT configuration sources from nbiot_ to NB-IoT_ to be consistent with other NB-IoT developments.
- various bugs fixed:
  - try to avoid "buffer full" problem when pushing DL traffic
  - add a stop_rf function in the RU
  - cleanup - remove unnecessary calls to get_cpu_freq_GHz
    (was disrupting realtime at startup, generating lots of UU and LL)
  - cleanup MAC PDU generation

Compilation with Rel10 is not functional anymore.
Compilation of unitary simulator is not functional anymore.