'RELENG_5_3_0_RELEASE'.

This commit was manufactured to restore the state of the 5.3-RELEASE image.

simple errx() function.
Improve behavior when bzlib/zlib are missing by detecting and
issuing an error message on attempts to read gzip/bzip2 compressed
archives.

in the regular ustar header that are overridden by the pax
extended attributes.  As a result, it makes perfect sense to
use numeric extensions in the regular ustar header so that readers
that don't understand pax extensions but do understand some other
extensions can still get useful information out of it.

This is especially important for filesizes, as the failure to
read a file size correctly can get the reader out of sync.

This commit introduces a "non-strict" option into the internal
function to format a ustar header.  In non-strict mode, the formatter
will use longer octal values (overwriting terminators) or binary
("base-256") values as needed to ensure that large file sizes,
negative mtimes, etc, have the correct values stored in the regular
ustar header.

Mostly, these were being used correctly even though a lot of
variables and function names were mis-named.

In the process, I found and fixed a couple of latent bugs and
added a guard against adding an archive to itself.

push extract data down into archive_read_extract.c and out
of the library-global archive_private.h; push dir-specific
mode/time fixup down into dir restore function; now that the
fixup list is file-local, I can use somewhat more natural
naming.

Oh, yeah, update a bunch of comments to match current reality.

 * New read_data_block is both sparse-file aware and uses zero-copy semantics
 * Push read_data_block down into specific formats (opens door to
   various encoded entry bodies, such as zip or gtar -S)
 * Reimplement read_data, read_data_skip, read_data_into_fd in terms
   of new read_data_block.
 * Update documentation
It's unfortunate that I couldn't just call the new interface
archive_read_data, but didn't want to upset the API that much.

certain flags set (e.g., schg or uappend) would fail because the flags
were restored before the hardlink was created.

To address this, I've generalized the existing machinery for deferring
directory timestamp/mode restoration and used it to defer the
restoration of highly-restrictive flags to the end of the extraction,
after any links have been created.

Pointed out by: Pawel Jakub Dawidek (pjd@)

during lengthy extract operations.

Pointed out by: Simon Nielsen

provide an interface for the client to query this information.