USRP addressess and clock sources can be configured in the configuration file with the RU section with comma separated IP addresses in 'sdr_addrs' and with strings "internal"/"external"/"gpsdo" in 'clock_src'.

TODO: Currently the driver picks the two first RX and TX channels when nb_tx and nb_rx are both set to 2. If a developers wants to force usage of two devices, 'set_rx_subdev_spec' and 'set_tx_subdev_spec' can be used to indicate to the driver so that antennas from separate devices will be used. To rephrase: until 4 antennas are supported by OAI, testing with two devices, so that antennas from both devices are used, requires manual configuration of which subdevices' antennas are used.

Conflicts:
	targets/ARCH/USRP/USERSPACE/LIB/usrp_lib.cpp

remove compilation warnings, especially when disabling T_TRACER. enhance LOG_M macro implementation, introduce LOG_DEBUG_XXX macro to replace #ifdef DEBUG_XXX

log.c simplification, fix usefull functionality which never worked, move all log code from openair2 to common

Log review step 1: legacy VCD removal, LOG macro modified, TTracer enabled at build time by default, in a way it, by default configuration,  provides console logs, as in previous versions

1. It's no need to modify LTE-RRC's ASN.1 file for enabling option group
   feature in generate_asn1.
2. It's no need to patch the C header files generated from
   LTE-RRC/S1AP/X2AP's ASN.1 in fix_asn1.
3. It's no need to pre-process S1AP/X2AP's ASN.1 for enabling information
   object class feature by asn1tostruct.py.

This commit requires an un-official version of asn1c which are
collaboration of asn1c community members and `build_helper` is modified
in this commit accordingly :

  https://github.com/brchiu/asn1c/tree/velichkov_s1ap_plus_option_group

This asn1c can also convert ASN.1 of 5G NR RRC (38.331, v15.1.0) and
generate C files with -findirect-choice command line option without
tweaking ASN.1 file.

Examples for how to use this asn1c for S1AP are in S1AP files, e.g.
s1ap_eNB_nas_procedures.c and s1ap_eNB_handler.c.

There is an modified openair-cn (based on tag 0.5.0) with this new asn1c at :

  https://github.com/brchiu/openair-cn/tree/new-asn1c

Basic S1AP interaction and data transfer operation between OAI eNB and
this modified openair-cn has been tested.

Note: Community version of asn1c is keeping evolved to provide better usage.

Remove compilation warnings, also fix telnet server compilation failure and NB-IoT shared lib compilation failure introduced when reviewing L1 sources  organization

(cherry picked from commit 71dacd44)

This commit reverts the change coming from
675fd0af.

On a test machine, running the basic simulator (both eNB, UE
and T tracer) with 100 RBs eats too much of memory on a computer
with 8GB of RAM, leading to a reboot because the computer
was not responsive anymore.

Other solutions are needed to solve the memory issues, but
multiplying by 50 this number is not a good one, at least
not in the basic mode of operation. If this value needs
to be that big, a #ifdef #else #endif may be used.

May not be the best solution. Maybe we can pass -DXX=XX
on the command line somehow.

20 was wrong, it means 2 dB.

200 is a bit high on my setup. Today the code hardcodes the noise
level as 30dB and a target of 20dB above noise is chosen by default.
Some more work is needed to estimate the real noise level. Some
more work is needed to set proper defaults.

Since now pucch_n1_AN is taken from the configuration file,
it has to be set to 0. Value 32 will not work well, at least
in FDD. This has to be handled properly at some point
(do not use uplink resource blocks used by PUCCH for PUSCH).