Previously pigz would return an exit code of 0 if there were no
serious errors, e.g. I/O errors or insufficient memory. Now pigz
will return 1 if it encounters any issues, such as invalid or
unrecognized compressed data, file names without the expected
suffix, trying to overwrite a file, etc. Since pigz can process
multiple input files, it will return an exit code of 0 if there
were no issues, and will return an exit code of 1 if one or more
of the inputs had an issue.

An empty suffix with forced compression would result in both the
original and compressed file being deleted.

Avoid warning for ignoring chown() return value on some glibc's,
and change compiler from cc to gcc. Sometimes the (void) before
chown() is not sufficient to signal the programmer's intent to
ignore the return value. (Thank you return-value police.) This
commit kills that gcc warning just for copymeta(). Using pragma
then required ignoring a warning for versions of gcc that don't
recognize it (when using -Wall). Finally, gcc is used instead of
cc for platforms that don't make that equivalency.

This adds an option present in gzip to improve interoperability.

Change command line processing to go through all of the options
and associated parameters first, and then go through the command
line again, processing the file names using the resolved options.
In addition, if "-" follows a "--", then consider the "-" to be
a file name instead of stdin. Both of these changes are to be more
compatible with gzip, and are not compatible with the previous
versions of pigz, which would process the options and file names
in the sequence they appear.

Use // comments througout, improve comments style, move opening
braces to function definition lines.

This also cleans up the termination of the read thread for those
cases where the entire input was not read, but the read thread is
no longer needed.

This allows for weak linking with a zlib library whose version is
older than the zlib header file used to compile pigz. The version
is checked at run time, and deflatePending() is not called if the
linked library does not have it. This commit adds a check as well
when invoked for the earliest acceptable version of zlib (1.2.3).

BSD make doesn't understand $^, and the Sun make has a problem with
$<. This avoids the automatic variables by explicitly specifying
the objects and targets. This also avoids a compiler complaint for
a #error directive by putting the message in quotes.

Facilitate compiling pigz without Zopfli for implementations that
do not need it and that desire to minimize the code size.

This replaces the previous -M for --maxsplits with -J. (Hopefully
no one was using -M. Probably not.) This fills a hole left by the
change of -n, --no-name to also not store/restore the modification
time. Now -nM will store/restore the modification time, but not
the name. The full set of combinations is -n for neither, -N for
both, -nM for just the time, and -Nm for just the name. Note that
the order is important. -n or -N will overwrite the effect of a
preceding -m or -M. The default for compression is -N, and the
default for decompression is -n. So -N or -n can be left off for
those cases, respectively.

Though this is not consistent with the name of the option, this
commit makes pigz compatible with gzip's use of -n and --no-time.

Apparently gzip has supported -m all along to not include the
modify time, but it wasn't in the command help list. This commit
adds -m as an alias for --no-time. -T is retained as an alias for
--no-time for backwards compatibility with previous versions of
pigz.

Microsoft has not implemented and refuses to implement C99 aspects
that are not also part of C++11 or later C++ standards. (Note that
the "99" in C99 refers to 1999. That was the year my younger son
was born, who is now applying for college.)

Before -K would fail when the compressed or uncompressed data, or
the offset of the central directory, was 4 GiB or more. Now -K
will use Zip64 data descriptors in the local and central headers,
and will use the Zip64 end records as needed.

pigz currently will not generate a ZIP64 format .zip file if the
input uncompressed or compressed lengths are greater than or equal
to 4 GiB. This commit issues a warning in that instance that the
resulting .zip file will be unusable.

This off-by-one error resulted in useless reexamination of the
same files by descending twice into each directory.

The consistency of block sync markers depends on zlib 1.2.6 or
later. pigz -vV will display the zlib version linked with pigz.

This forces two sync markers between independent blocks, giving a
nine-byte signature 00 00 ff ff 00 00 00 ff ff to search for when
processing compressed data in parallel.