implement --version option according to GCS

[Bruno Haible]

These patches implement a --version option for some of the build-aux/* programs
according to the GNU Coding Standards
  <https://www.gnu.org/prep/standards/html_node/_002d_002dversion.html>

I concentrated on the programs that are likely invoked interactively.
Adding --help and --version to helper scripts (such as config.libpath, 
config.rpath,
declared.sh, install-reloc, etc.) is not high priority to me.

The same thing would be useful also in these two scripts, but I didn't succeed.
Help appreciated!
  * update-copyright: This would require removing the '-pi' option and using a
    'while (<>)' loop. But I didn't succeed. Some p*rl magician is needed.
  * vcs-to-changelog.py: How to tell 'argparse' that there are no required
    parameters when --help is given?


2021-04-11  Bruno Haible  <bruno@clisp.org>

        useless-if-before-free: Implement --version option according to GCS.
        * build-aux/useless-if-before-free (copyright_year): New variable.
        (GetOptions): Print also a short copyright and license notice and
        author statement.

        libtool-next-version: Implement --version option according to GCS.
        * build-aux/libtool-next-version (scriptversion): New variable.
        (func_version): Deduce the copyright year from it. Terminate sentences
        with '.'.

        gnupload: Implement --version option according to GCS.
        * build-aux/gnupload (copyright_year, copyright): New variables.
        (--version): Print also a short copyright and license notice.

        git-version-gen: Implement --version option according to GCS.
        * build-aux/git-version-gen (version): State the license. Use wording
        from GCS.

        bootstrap: Implement --version option according to GCS.
        * build-aux/bootstrap (copyright_year, copyright): New variables.
        (--version): New option processing.

        announce-gen: Implement --version option according to GCS.
        * build-aux/announce-gen (copyright_year): New variable.
        (GetOptions): Print also a short copyright and license notice and
        author statement.

0001-announce-gen-Implement-version-option-according-to-G.patch
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0002-bootstrap-Implement-version-option-according-to-GCS.patch
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0003-git-version-gen-Implement-version-option-according-t.patch
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0004-gnupload-Implement-version-option-according-to-GCS.patch
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0005-libtool-next-version-Implement-version-option-accord.patch
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0006-useless-if-before-free-Implement-version-option-acco.patch
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