add SIGINFO support.

apply a change from Xin LI <delphij@delphij.net> to avoid problems when
reading from pipes. introduced with the multi-part bz2 fixes.

fix support for multi-section bzip2 files, as created by pbzip2.

branches: 1.11.6; 1.11.12;
Remove clause 3 and 4 from TNF licenses

branches: 1.10.16;
Add standard TNF copyright boilerplate.

apply a patch from onno van der linden in PR#32070 that fixes
these problems:
1) gzip -vt just prints the contents of a .Z file
2) gzip -vt will print OK even if the .gz file is corrupt
3) gzip -vt prints nothing with a .bz2 file
4) gzip can loop endlessly with a corrupt .bz2 file

fix signed/unsigned mismatch reported by Christian Biere in PR#31180
using his provided patch.

Fix numerous uninitalized variables.
Detected with gcc -Wuninitialized.

branches: 1.6.2;
The last commit slightly increased the size of gzip - I had thought that
all the install media used the 'SMALL' variant, but this is not the case.
Redo the percentage print code to reduce the size to less than the old version.
Fix another fd leakage (didn't call fclose() if ferror() returned non-zero.
Change some maybe_warn() to maybe_warnx() in places I'm sure errno is undefined.
Call mayber_warn() earlier in other paths so that errno might still be valid.
Make the SMALL and NO_BZIP/COMPRESS_SUPPORT options all compile with WARNS=3.

- fix "gzip -t" to not output anything by default. PR#25507
- fix any decompression on corrupted gzip files. PR#25508
- ask to overwrite files if we have a tty, rather than failing the
operation. PR#25509.
- clean up maybe_err()/maybe_warn(): use maybe_err() only for fatal
errors. maybe_warn() is for processing errors. this allows
"gzip -d file1.gz file2.gz" to decompress file2.gz even if file1.gz
is corrupted, etc.
- change the internal compressor/decompressor API to return "-1" on
failure, not 0. this allows for 0-sized files to be decompressed
correctly.

significantly rototill. don't use the high-level gzio functions
anymore, use the low-level inflate()/deflate() directly. this
allows support file-type detection on stdin; now can decompress
.Z and .bz2 files fed to stdin (fixes PR#25192) additionally it
makes -v work with stdin or stdout (fixes PR#25215.)

(with these changes, we no longer need gzopenfull(3) in libz.)

thanks to martin@ for the code gzip.c:gz_uncompress() is based on.

backout previous. fix the bug it inspired instead. we will want this
version of the code when doing file-type detection.

patch from tron@ to convert to using public bz interfaces. simonb says
no reason not to and this fixes PR#24964.

branches: 1.1.2;
port simonb's bzip2 support.
misc cleanups.