libpipeline: Update to version 1.5.7

libpipeline: Update to version 1.5.7

- Update from 1.5.6 to 1.5.7
- Update of rootfile
- Changelog
    Version: 1.5.7
	  * lib/Makefile.am (libpipeline_la_LDFLAGS): Bump -version-info to 6:7:5.
	Make socketpair configure tests compatible with C23
	K&R-style zero-argument function definitions will no longer be
	 permitted.
	  * m4/pipeline-socketpair.m4 (PIPELINE_SOCKETPAIR_PIPE,
	    PIPELINE_SOCKETPAIR_MODE): Use `int main(void)`, not `int main()`.
	  * NEWS.md: Document this.
	Update pre-commit hooks
	  * .pre-commit-config.yaml (pre-commit-hooks): Update to v4.3.0.
	    (clang-format): Update to v14.0.6.
	Update manual page date
	  * man/libpipeline.3 (.Dd): Update to the date of the last substantial
	    modification.  Leaving this as 2010 suggested more antiquity than we
	    need to suggest.
	Update home page URL
	  * README.md: Use `https://libpipeline.gitlab.io/libpipeline/`.
	  * lib/libpipeline.pc.in (URL): Likewise.
	web: Update last release
	  * web/index.html: Update to 1.5.6.
	web: Fix last-modified date generation
	  * .gitlab-ci.yml: Replace `@DATE@` with the current date in
	    `public/index.html`.
	  * web/index.html: Use `@DATE@` template.
	web: Assorted URL updates
	  * web/index.html: Update Git URLs to GitLab.  Chase various redirects
	    and/or switch to HTTPS.  Remove old Savannah link.
	Add GitLab Pages site
	  * .gitlab-ci.yml (stages): Add deploy.
	    (pages): New job.
	  * web/index.html, web/libpipeline-lightning-talk.odp, web/standard.css,
	    web/white.css: New files.
	Transferred Git repository to new group
	  * README.md: Change GitLab URL to
	    https://gitlab.com/libpipeline/libpipeline.
	  * NEWS.md: Document this.
	Add notes to libpipeline(3) of when functions were added
	  * man/libpipeline.3 (DESCRIPTION, ENVIRONMENT): Add various "Added in"
	    notes.
	  * NEWS.md: Document this.

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Reviewed-by: Michael Tremer <michael.tremer@ipfire.org>