adding RRU/Fronthaul functionality to oaisim

cmake_targets/CMakeLists.txt

cmake_targets/build_oai

openair1/PHY/defs.h

targets/ARCH/ETHERNET/USERSPACE/LIB/ethernet_lib.c

targets/RT/USER/lte-enb.c

targets/RT/USER/lte-softmodem.c

targets/RT/USER/lte-ue.c

targets/SIMU/USER/oaisim.c

targets/SIMU/USER/oaisim_functions.c