Fix libxc 6.2.x support; refresh v7.1 headers from released 7.1.2 (v0.1.3) - #1

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/