This provides two functions: get_meas_rep_avg() to obtain the sliding
window average of one particular field, and meas_rep_n_out_of_m_be()
to check if at least N out of M measurments are >= BE.
Since we are keeping a bitvec of the neighbor cells, we can now use
bitvec_get_nth_set_bit() to determine the ARFCN for each reported
cell in the 04.08 MEASUREMENT REPORT.
This patch extends struct gsm_meas_rep into a complete structure containing all
information from both uplink and downlink measurement results/reports.
This is a first step to provide this complete measurement data as a C structure
into a to-be-implemented handover decision algorithm.