frame synchronization mechanism and robustification of if4p5 packet handling for out-of-order asynchronous reception (PDLFFT)

debugging information in lte-enb, addition of external reference option in lte-softmodem and usrp_lib.cpp

usrp 20 MHz on 30.72 master clock. fixed memory leak in prach.c for 20 MHz with 3/4 sampling. added default attributes to threads in lte-enb.c

usrp_lib: setting master clock rate to 30.72 and filter to 20MHz for all cases to improve noise figure and channel response

UHD interfacing (master clock 30.72, bandwidths on 5/10/20 @ 20 MHz), RX gain calibration back to normal.

changes in BSR handling in eNodeB. UL throughput on 5 MHz is 8 Mbit/s (mcs 19, 20 PRB). MCS 20 is not working for an unknown reason.

make changes to use the fronthaul configuration parameters - updates to rrh_gw.c and eNB_transport.c wrt to changes in openair0_device struct

minor changes in openair_device structure (naming of fields), calibration information for X310 timing, some initializations from lte-softmodem.c for USRP moved to usrp_lib.cpp