Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Clean up tools in tools/tools/netrate.

- tcpconnect incorrectly uses err() in usage() with errx() semantics [1]
That produces dirty error message:
tcpconnect: usage: tcpconnect [ip]: Unknown error: 0
- 64-bit aware fixes in printf() usage [2]
o netrate/juggle: time_t has arch-dependent size
o netrate/tcpconnect: don't assume %ll has always 64bit.

PR: 146088 [1], 146086 [2] (modified)
Approved by: kib (mentor)
MFC after: 1 week

Add simple TCP connect and TCP receive benchmark components, intended to
measure the rate of TCP connection round trips supported by a host at
the socket layer.