Allow phpunit 9 & update doctrine/inflect to ^2.0

[DanielGSoftware]

Our company wants to upgrade to Laravel 9, but certain dependencies need to be allowed.

• Doctrine 1.4 and 2.0 are not compatible with each other, so I set the minimum version to ^2.0. This will automatically make the minimum php version required to 7.2. I went through the code and fixed the breaking changes.

• We also need to allow php-unit 9, but this is not compatible with phpunit 5 and is from version 6 or higher. Also fixed all breaking changes.

Tests succeed: https://github.com/DanielGSoftware/xsd2php/pull/1

[goetas]

thanks a lot for this :tada:

[DanielGSoftware]

@goetas You're welcome, and thank you for this package :)! Can you also make a new tag for this? (I think we need to tag a 1.0.0 version because of dropped support for php 7.1)

I also noticed that CI isn't working properly if I'm correct, if you want to switch over to Github actions, I can make a PR with a script if you'd like

[goetas]

having github actions would be great! thanks a lot

I will create a new tag, dropping dependencies is not a BC break, so a usual increment is ok