Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Fixed error checking of pthread(3) functions.

PR: 143807
Submitted by: pluknet (partly)

Enforce the compile-time threads limit at run-time, so that a high thread
count argument doesn't cause a segfault or memory corruption when the
compile-time array is overrun.

Add multi-process support to simple http micro-benchmark, now the default.
Use -t for thread support. Also added are -n to specify number of threads
or process, and -s to set the length of the test.

Change u_int64_t to uintmax_t and use %ju, so it compiles on 64bit archs.
I changed every u_int64_t to uintmax_t, as we should use eventually
uint64_t anyway those days.

Don't hard-code port numbers, let the user specify them.

Add basic simplified HTTP benchmark tools to the netrate suite:

- http is a lightweight, multithreaded HTTP query tool, which performs
a timed measurement of the rate at which it can download files using
single-fetch HTTP/1.0. Other than specifying the IP and a URL path,
it requires zero configuration.

- httpd is a lightweight, multithreaded HTTP server tool, which exports
a single file of choice to the HTTP client, and responds with it no
matter what the request. Other than specifying the file to export,
it requires zero configuration.

The goal of these tools is to measure the network costs associated with
HTTP serving, rather than file system, HTTP protocol parsing, error
handling, etc, and as such, parts relating to less interesting components
of HTTP testing are intentionally omitted. Both are linked against
libpthread by default.