Release Exiv2 version 0.28.7 (backport #3380)

[mergify]

Update version numbers for the new release.

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This is an automatic backport of pull request #3380 done by Mergify.

[mergify]

Cherry-pick of 7465595 has failed:

On branch mergify/bp/main/pr-3380
Your branch is up to date with 'origin/main'.

You are currently cherry-picking commit 7465595b.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   CMakeLists.txt
	both modified:   SECURITY.md
	both modified:   doc/ChangeLog
	both modified:   meson.build

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally