Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

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

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

Spelling fixes for tools/

Add some $FreeBSD$ tags so svn will allow the commit.

Add open_to_operation, a security regression test that opens files with
various open flags and then tests various operations to make sure that
they are properly constrained by open flags. Various I/O mechansms
are tried, including aio if compiled into the kernel or loaded as a
module. There's more to be done here but it's a useful start, running
about 220 individual tests.

This is in support of FreeBSD-SA-08:03.sendfile.