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

Fix warnings with gcc 5.0

reconnect.c:
- Convert the K&R prototype of main to an ANSI prototype to mute a
warning from gcc 4.2.1
- Close s_sock2 after finishing off the last test to plug a leak and
mute a warning from gcc 5.0 about a -Wunused-but-set variable

sendfile.c:
- Fix a -Wunused-but-set warning with gcc 5.0 with pagesize in main(..)

MFC after: 5 days
Sponsored by: EMC / Isilon Storage Division

- Don't use /tmp because it's outside ATF's prescribed sandbox
- Replace a hardcoded PATH_MAX value with sizeof(path)
- Use path like an array, not a pointer, and always try to unlink it in cleanup

MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division

Add a sendfile regression test for transmit length > file size.

This test identified the issue fixed in FreeBSD-SA-13:11.sendfile.

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

Allow to specify path to a file we want to test with sendfile(2).
This allows to specify selected file system and not only /tmp/.

Update the sendfile regression test so that it outputs results in the
TAP format.
Add a checksum to verify that the data hasn't been corrupted between
being read from disk and being received.

Approved by: rrs (mentor)

o Correct a comment: a test file size is a four pages not three.

Test sending 0 bytes.

Fix length calculation.

Valid error codes for err() and errx() are 1..255.
The correct format specifier for ssize_t is %zd.

Add more tests to verify last sendfile(2) breakage: test sending more
than a page size and nbytes=0.

Add a basic regression test for sendfile() over TCP, which sends varying
lengths of headers and data and makes sure it receives about the right
number of bytes.