Support for PHP7.1 (min.)

[Progi1984]

Description

Support for PHP7.1 (min.)

Checklist:

• I have run composer run-script check --timeout=0 and no errors were reported
• The new code is covered by unit tests (check build/coverage for coverage report)
• I have updated the documentation to describe the changes

[PowerKiKi]

Supporting old EOL PHP version goes against https://phpspreadsheet.readthedocs.io/en/latest/#php-version-support and the recent #2297. This also hinder adoptions of new PHP features in our codebase (typehint would be extra-nice), and complexify the whole maintenance work.

Why did you need to add back support for very old EOL PHP versions ?

[Progi1984]

@PowerKiKi The support that you share the link is about PhpSpreadsheet. I try for PhpWord & PhpPresentation to have the max support for it. My customers have this need and pay for this support.

[PowerKiKi]

I was not aware you have customer paying for support of old PHP version. I restored a few more things via #2314.

I meant to release a 1.0.0, following b9f1151, to help folks in #2239. Also to clearly communicate that this project has been production ready for a very long time. And despite the roadmap to v1 being incomplete. Is that OK with you ?