cellar-cli-c: client CLI di Cellar reimplementato in C (statico, retrocompatibile)

Reimplementazione fedele di cellar-cli.py (enne2/cellar @ f5216b1) in C99
POSIX.1-2008, mono-thread, senza dipendenze esterne: miniz e' vendored per
deflate/inflate raw, mentre contenitore gzip, multipart/form-data in streaming,
tar PAX/ustar, JSON e client HTTP/1.1 sono scritti a mano.

- 7 comandi (list, upload, download, install, scan-local, wizard-upload,
  wizard-install) con stdout/stderr/exit code identici al client Python
- 30/30 test di parita' (tests/parity_test.sh) contro due server mock
  indipendenti: output a confronto, alberi installati, interop tar con
  tarfile di Python e con GNU tar, archivio C equivalente a quello Python
- build statiche x86-64 / i686 / aarch64: nessun simbolo GLIBC richiesto,
  nessuna syscall moderna (statx/openat2/memfd_create/getrandom), LFS 64 bit,
  resolver DNS di riserva (hosts + query UDP) per glibc statica senza NSS
- miglioramento rispetto all'originale: upload multipart in streaming invece
  di leggere l'intero archivio in RAM
- divergenze volute documentate nel README (help piu' sintetico, mtime dei
  symlink non ripristinato come tarfile, EOF nei prompt, niente TLS)

Build: make | make 32 | make arm64 | make test | make verify

third_party/miniz.LICENSE

@@ -0,0 +1,22 @@
+Copyright 2013-2014 RAD Game Tools and Valve Software
+Copyright 2010-2014 Rich Geldreich and Tenacious Software LLC
+
+All Rights Reserved.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.