address and port histograms have bar labels

above each bar in the histograms, a label is now printed at 45 degrees
IPv6 addresses are shown at half font size
labels are black unless there's a special color for the bar

redid port and address histogram padding to accommodate bar labels

created operator== for rgb_t
added float-comparing epsilon to rgb_t as 1/256
histogram bug fixes

dst_addr_histogram no longer prints raw pointers for top 3
Fixed port_histogram not counting segments it ingests