Display OS information in the summary line

This commit extends the _daemons struct for API information,
and prints OS info in the summary line. For example:

\#   0 S: localhost (Linux 3.11.0-rc2aha+), random seed: 3789404117, sbuf = 16384/0, rbuf = 87380/0 (real/req), SMSS = 65468, Path MTU = 65520, Interface MTU = 65536 (unknown), flow duration = 10.000s/10.000s (real/req), through = 11674.676753/0.000000Mbit/s (out/in), request blocks = 1781420/0 (out/in)
\#   0 D: localhost (Linux 3.11.0-rc2aha+), random seed: 3789404117, sbuf = 16384/0, rbuf = 87380/0 (real/req), SMSS = 21888, Path MTU = 65520, Interface MTU = 65536 (unknown), through = 0.000000/11674.658181Mbit/s (out/in), request blocks = 0/1781412 (out/in), IAT = 0.002/0.006/0.398 (min/avg/max)