MFC r311572, r311895, r311928, r311985, r312395, r312417

MFC r311572, r311895, r311928, r311985, r312395, r312417

r311572:
Fix file descriptor leaks in cmp(1)

Also, add a few test cases

Reported by:	Coverity
CID:		271624 275338
Reviewed by:	ngie
MFC after:	4 weeks
Sponsored by:	Spectra Logic Corp
Differential Revision:	https://reviews.freebsd.org/D9074

r311895:
Fix memory leaks during "tail -r" of an irregular file

* Rewrite r_buf to use standard tail queues instead of a hand-rolled
  circular linked list. Free dynamic allocations when done.
* Remove an optimization for the case where the file is a multiple of 128KB
  in size and there is a scarcity of memory.
* Add ATF tests for "tail -r" and its variants.

Reported by:	Valgrind
Reviewed by:	ngie
MFC after:	4 weeks
Sponsored by:	Spectra Logic Corp
Differential Revision:	https://reviews.freebsd.org/D9067

r311928:
Fix build of usr.bin/tail with GCC

Submitted by:	pluknet
Reported by:	pluknet
MFC after:	27 days
X-MFC-with:	311895
Sponsored by:	Spectra Logic Corp

r311985:
Fix uninitialized variable CIDs in route6d

The variables in question are actually return arguments, but it's still good
form to initialize them.

Reported by:	Coverity
CID:		979679 979680
MFC after:	4 weeks
Sponsored by:	Spectra Logic Corp

r312395:
Fix several Coverity CIDs in devd

CID 1362055, 1362054: File descriptor leaks during shutdown
CID 1362013: Potential null-termination fail with long network device names
CID 1362097: Uncaught exception during memory pressure
CID 1362017, 1362016: Unchecked errors, possibly resulting in weird behavior
	if two devd instances start at the same time.
CID 1362015:	Unchecked error that will probably never fail

Reported by:	Coverity
CID:	1362055 1362054 1362013 1362097 1362017 1362016 1362015
MFC after:	4 weeks
Sponsored by:	Spectra Logic Corp

r312417:
Fix build of devd with GCC 4.2

Reported by:	olivier
Pointy-hat-to:	asomers
MFC after:	27 days
X-MFC-with:	312395
Sponsored by:	Spectra Logic Corp

git-svn-id: svn://svn.freebsd.org/base/stable/10@314425 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f