usr.sbin: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

imgact_binmisc: Optionally pre-open the interpreter vnode

This allows the use of chroot and/or jail environments which depend on
interpreters registed with imgact_binmisc to use emulator binaries from
the host to emulate programs inside the chroot.

Reviewed by: imp
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D37432

binmiscctl: Avoid segfault with "binmiscctl add" and no extra params

MFC after: 1 week

binmiscctl(8): miscellaneous cleanup

- Bad whitespace in Makefile.
- Reordered headers, sys/ first.
- Annotated fatal/usage __dead2 to help `make analyze` out a little bit.
- Spell a couple of sizeof constructs as "nitems" and "howmany" instead.

MFC after: 1 week

Don't leak resources on duplicate -m or -M arguments. Last one wins.

CID: 1204385, 1204384

binmiscctl should use modfind instead of kldfind

kldfind() only matches kernel modules, so if you link imgact_binmisc directly
into the kernel, binmiscctl can't find it, tries to load it, and errors
out with:
Can't load imgact_binmisc kernel module: File exists

A quick search of other base commands shows that the correct procedure is to
call modfind(), and then try kldload() if that fails.

PR: 218593
Submitted by: Dan Nelson <dnelson_1901@yahoo.com>
MFC after: 1 week

Another attempt at resolving CID 1305629. The test of cmd == -1
may make Coverity think that other negative values of cmd (used
as an index) are possible. Testing < 0 is a more common idiom
in any case.

Reported by: Coverity
CID: 1305629

Revert r299584:
Mark usage() as __dead2 so that Coverity doesn't think that execution
continues after the call and uses a negative array subscript.

Requested by: bde

Mark usage() as __dead2 so that Coverity doesn't think that execution
continues after the call and uses a negative array subscript.

Reported by: Coverity
CID: 1305629

If no arguments are passed to a subcommand that requires arguments,
error out before we deref a null pointer in the check for max length.

Thanks to otis in IRC for the bug report.

MFC after: 3 days

Check for invalid length or more than max length for the interpreter, instead
of the validity of the string pointer holding the interpreter.

Submitted by: sson
Reviewed by: dim
MFC after: 3 days

Add Stacey Son's binary activation patches that allow remapping of
execution to a emumation program via parsing of ELF header information.

With this kernel module and userland tool, poudriere is able to build
ports packages via the QEMU userland tools (or another emulator program)
in a different architecture chroot, e.g. TARGET=mips TARGET_ARCH=mips

I'm not connecting this to GENERIC for obvious reasons, but this should
allow the kernel module to be built by default and enable the building
of the userland tool (which automatically loads the kernel module).

Submitted by: sson@
Reviewed by: jhb@