MFC bspatch Capsicumization and improvements

r304691: bspatch: apply style(9)

Make style changes (and trivial refactoring of open calls) now in order
to reduce noise in diffs for future capsicum changes.

r304807 (allanjude): Capsicumize bspatch

Move all of the fopen() and open() calls to the top of main()

Restrict each FD to least privilege (read/seek only, write only, etc)

cap_enter(), and make all except the output FD read/seek only.

r304821: bspatch: remove output file in the case of error

r305486: bspatch: add sanity checks on sizes to avoid integer overflow

Note that this introduces an explicit 2GB limit, but this was already
implicit in variable and function argument types.

This is based on the "non-cryptanalytic attacks against freebsd
update components" anonymous gist. Further refinement is planned.

r305737: bspatch: remove superfluous newlines from errx strings

r305822: bspatch: use #define for header size instead of magic number

r306026: bspatch: Remove backwards-compatibility sys/capability.h support

bspatch previously included sys/capability.h or sys/capsicum.h based
on __FreeBSD_version, as FreeBSD is the upstream for bsdiff and we may
see this file incorporated into other third-party software.

The Capsicum header is now installed as sys/capsicum.h in stable/10 and
FreeBSD 10.3, so we can just use sys/capsicum.h and simplify the logic.

MFC r264823 (ed): Make usage printing more consistent with other tools.

- Introduce a separate usage() function.
- Don't use argv[0]. Directly name the application, as we do elsewhere.
- Don't prepend the application name.
- Don't print two newlines.

Also apply the unnecessary semicolon cleanup from r298089

Fix bspatch heap overflow vulnerability.

Obtained from: Chromium
Reported by: Lu Tung-Pin
Security: FreeBSD-SA-16:25.bspatch

MFC: r290329,r290336
PR: 204230

r290329:

Use meaningful errno for ssize_t overflow in read().
Catch size_t overflow in malloc().

r290336:

Check for (old|new)size + 1 overflows off_t.

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

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

Remove trailing whitespace per mdoc lint warning

Disussed with: gavin
No objection from: doc
Approved by: joel
MFC after: 3 days

Silence bogus warning when compiling with gcc46:
error: 'pos' may be used uninitialized in this function

Reviewed by: cperciva
Approved by: dim
MFC after: 3 days

mdoc: move CAVEATS, BUGS and SECURITY CONSIDERATIONS sections to the
bottom of the manpages and order them consistently.

GNU groff doesn't care about the ordering, and doesn't even mention
CAVEATS and SECURITY CONSIDERATIONS as common sections and where to put
them.

Found by: mdocml lint run
Reviewed by: ru

Build usr.bin/ with WARNS=6 by default.

Also add some missing $FreeBSD$ to keep svn happy.

Add notes pointing out that bsdiff does not store file hashes and
bspatch thus does not verify file hashes, and that consequently it
is recommended that users store hashes separately and verify files
before and after running bspatch.

Requested by: BugMagnet
MFC after: 1 week

Portability fix for non-POSIX operating systems: Open files in binary mode.

PR: bin/106358
Submitted by: techtonik at php dot net

Fix up markup.

Include ../Makefile.inc, since without it programs get installed in the
wrong place.

Pointy hat to: cperciva

Add bsdiff and bspatch to the base system. These are tools for
constructing and applying binary patches; in particular, they perform
well (in the sense of constructing small patches) for executable code.
Both portsnap (coming to the base system Real Soon Now) and FreeBSD
Update (coming to the base system a bit later) use bspatch.

This is the same code as the bsdiff-4.2 which has been in the ports
tree (misc/bsdiff) for the past year, with the following exceptions:
1. The license is now the traditional 2-clause BSD;
2. Instead of forking and execing bzip2, the code now uses libbz2; and
3. Some minor changes have been made to fit this code into the base
system (adding $FreeBSD$ tags, putting bsdiff and bspatch into separate
directories, etc.)

This code is rather ugly and has lots of style bugs (mostly because I
wrote it before I had ever heard of style(9)). Some day I'll come
back and clean it up.

Discussed on: freebsd-arch
MFC before: 5.5-RELEASE
Tested by: Several million users (earlier version).