Develop integration w07

See merge request !116

Summary of changes:
- integration of branch tm4-fixes (feature-59-tm4 + somes fixes)
- integration of branch enhancement-199-nas-multi-ue
- integration of branch develop-realtime-lts
- integration of branch enhancement-211-snapping
- various bugfixes

Prior to this commit, the following command failed to build dlsim:
    ./build_oai --phy_simulators -c

Choice has been made to define it in a .h file as a static inline
function.

The command line to get the error was:
    ./build_oai --eNB -w EXMIMO -c

The command line to get the error was:
    ./build_oai --eNB -w EXMIMO -c

We now have 4 versions of T_HEADER:
 - bad quality C++ version with time
 - good quality C version with time
 - bad quality C++ version without time
 - good quality C version without time

The compilation line was:
    ./build_oai --eNB -w USRP

The file openairinterface5g/cmake_targets/log/lte-softmodem.Rel10.txt
has been checked and all LOG_X (and 'msg') warnings have been fixed.

Not sure that it's correct, but those #pragma seem
to be of no use for gcc. Let's remove them
completely.

When rebuilding oaisim, I had a failure because the target
link already exists. The -f flag forces the link to be done.

- some cleanup
- thread names to include UE Mod_id
- arg of UE_thread_rxn_txnp4 to be struct rx_tx_thread_data again
- sync in UE_thread_rxn_txnp4 to use instance_cnt_rxtx again
- UE_thread to call itti_send_msg_to_task with UE->Mod_id + NB_eNB_INST
  instead of INSTANCE_DEFAULT again

This may break the softmodem UE, to be tested.
The most problematic thing may be the synchronization.
I don't think it will impact the processing at all,
but I won't bet my shirt on it.

git show -p 58052152
to see what it's about

git show 157707b0
to see what it's about

- build script has ability to indicate location for downloading uhd images
- one simple wrapper to set environment variables and initiate another program (supposed to be lte-softmodem)

Many variables were changed that should not have been changed.

This reverts commit d31634c3.

Laurent Thomas had a problem on one machine with the build_oai
way of checking for nettle.

The problem with the alternative solution of including nettle/bignum.h
is that it is very unclear.

The problem with nettle is that the file nettle/config.h does not
exist for version 2. It was introduced in version 3.

We want to support both versions, but there is an API incompatibility.
So we need an #if #else mechanism.

The file nettle/bignum.h is present in both versions 2 and 3 and it
includes nettle/version.h in the version 3.

So by including this file, we can check for the existence of
NETTLE_VERSION_MAJOR (that comes from nettle/config.h) in the
code.

But as you can see, the reasoning is way too complex.

So it's better to keep the check in cmake_targets/CMakeLists.txt.

As long as we support version 2 this will be the way to go.

It is possible to force a given version in specific non-generic
customized environments.

Merge branch 'develop' of https://gitlab.eurecom.fr/oai/openairinterface5g into various-l2-fixes-187

Conflicts:
	openair1/PHY/LTE_TRANSPORT/if4_tools.c
	targets/ARCH/ETHERNET/USERSPACE/LIB/eth_udp.c
	targets/ARCH/ETHERNET/USERSPACE/LIB/if_defs.h
	targets/PROJECTS/GENERIC-LTE-EPC/CONF/rcc.band7.tm1.if4p5.25PRB.lo.conf
	targets/PROJECTS/GENERIC-LTE-EPC/CONF/rcc.band7.tm1.if4p5.50PRB.lo.conf
	targets/PROJECTS/GENERIC-LTE-EPC/CONF/rcc.band7.tm1.if4p5.50PRB.usrpb210.conf
	targets/PROJECTS/GENERIC-LTE-EPC/CONF/rru.band7.tm1.if4p5.25PRB.oaisim.conf
	targets/PROJECTS/GENERIC-LTE-EPC/CONF/rru.band7.tm1.if4p5.50PRB.oaisim.conf

Conflicts:
	targets/RT/USER/lte-enb.c
	targets/RT/USER/lte-softmodem.c
	targets/RT/USER/lte-ue.c

Memory was allocated which was "lost" because the
address of the block was put in a pointer that is
overwritten just after.

Discussing with Elena, the current commit is the correct
way to do things.

Those functions modify a global char array (a string).

Let's pass a buffer to those functions, so that it's
thread safe. The caller has been modified, with hopefully
a buffer big enough (still bigger than what was there before,
so should not break more than it did).

command run:
    dos2unix openair1/SIMULATION/TOOLS/taus.c

 Conflicts:
	openair1/SCHED/phy_procedures_lte_ue.c
	targets/RT/USER/lte-softmodem.c
	targets/SIMU/USER/oaisim.c
	targets/SIMU/USER/oaisim_functions.c