Introduced a new timer_thread within lte-ue. This thread is ticking the subframes and wakes up UE_thread function which is waiting on a condition variable for nfapi_mode=3 (phy_stub)

Introduce nfapi_mode variable to differentiate functionality between phy_stub_ue mode (nfapi_mode=3) and normal full stack mode (nfapi_mode!=3).

Added functions copying nfapi requests to UE_mac_inst + Substituted calls to phy_procedures_ue rx/tx with phy_stub functions triggering MAC layer Tx/Rx procedures at UE MAC. Changes within UE_thread_rxn_txnp4

update SidelinkUEInformation (UE's side), RRCConnectionReconfiguration (eNB's side), add rrc_ue_process_radioResourceConfig to process RPs and configure MAC/PHY

Added handling of HI_DCI0_config requests at UE MAC. Eliminated calls to PHY functions from utilized UE MAC functions (e.g., ue_send_sdu) to support phy_stub operation mode.

Updated handling of DL_config and Tx_req pdus in phy_stub_UE to be compliant with nfapi callback functions

Added MAC level state variable for the UE and control mechanisms to ensure the correct operation of the UE MAC state machine.

uplink data from ue received, corrected scheduling of DCI0/UPLINK_CFG.  Fails to correctly form (SFNSF) for PHICH ACK

Added remaining fill_harq indication functions + the functionality to handle ul_config request pdus arriving from nfapi-vnf: trigger the appropriate UE_MAC and fill_indication functions to prepare the UL_indications which will be put into the socket for transfer back to vnf. Main changes within phy_stub_UE().

Summary of changes:
- fix a bug with Timing Advance.
  This should improve the stability of the connection
  (for now, only the scenario with one connected UE works).
- use RRC Release 14.3
- add some T tracers, minor fixes for T

Conflicts:
	common/utils/T/.gitignore
	common/utils/T/tracer/Makefile

Sometimes when the user does ctrl+c to quit, it may not quit
if nothing comes on the socket. Closing the socket in the
signal handler fixes this.

Do not link the X stuff for tracers not needing it.

Later on, use this file with gtkwave.
To be used to check realtime behaviour of the system.