support for 64bit fq-rate

[bltierney]

Starting with Linux 5.x, fq pacing is now supported for speeds > 32G. see: https://patchwork.ozlabs.org/project/netdev/patch/[email protected]/ and https://kernelnewbies.org/Linux_5.1

This change is needed in iperf3 to support this:

sed -i -e 's/unsigned int fqrate/uint64_t fqrate/g' -e 's/Setting fair-queue socket pacing to %u/Setting fair-queue socket pacing to %"PRIu64"/g' src/iperf_tcp.c src/iperf_udp.c