Prepare v2.1; various small fixes on code, build system, docs, and version compatibility

[DDvO]

To help with OSS clearing and build chains, now switch to version 2.1.

On this occasion, various small fixes.

[Copilot]

Pull Request Overview

This PR prepares version 2.1 with various fixes targeting code quality, build system improvements, documentation updates, and OpenSSL version compatibility. The changes primarily focus on improving compatibility between OpenSSL 3.0 and earlier versions by using conditional compilation.

Key changes:

• Added version-specific compatibility for OpenSSL 3.0+ using X509_VERIFY_PARAM_get0_host() instead of custom host storage
• Fixed variable scope and type issues in logging and parsing functions
• Updated build system requirements and version numbers across configuration files

Reviewed Changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/libsecutils/src/util/log.c	Moved variable declaration into debug scope and fixed type for string length
src/libsecutils/src/credentials/verify.c	Removed obsolete comment about OpenSSL API limitations
src/libsecutils/src/credentials/store.c	Added OpenSSL version guards for host storage and updated function signatures
src/libsecutils/src/credentials/credentials.c	Fixed function signature formatting
src/libsecutils/src/credentials/cert.c	Changed parameter type from long to int
src/libsecutils/src/connections/http.c	Added macro for backward compatibility with OCSP_parse_url
src/libsecutils/src/connections/conn.c	Added new IP address validation function
src/libsecutils/include/secutils/credentials/store.h	Updated function signatures to use const pointers
src/libsecutils/include/secutils/credentials/credentials.h	Fixed function signature formatting
src/libsecutils/include/secutils/credentials/cert.h	Changed parameter type from long to int
src/libsecutils/include/secutils/connections/conn.h	Replaced macro with function call for IP address check
debian/control	Updated dependency version to 2.1
debian/changelog	Added changelog entry for version 2.1
README.md	Updated tested tool versions and clarified Debian package building
Makefile_v1	Updated VERSION to 2.1
CMakeLists.txt	Updated minimum CMake version, project version, and improved OpenSSL detection

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[rajeev-0]

LGTM

[DDvO]

Thank you @benjamin-schilling and @rajeev-0 for your reviews.

I've just released libSecUtils 2.1, including the respective version tag.