Compatibility with Xdebug 3.0.0

[gggeek]

In PHPUnit/Extensions/SeleniumCommon/prepend.php there is usage of the XDEBUG_CC_UNUSED constant, which has been removed from xdebug 3.0

[gggeek]

ok, so it seems that XDEBUG_CC_UNUSED is not 'completely' doppped - but that it is only defined when xdebug mode includes code coverage... which is a bug fixed apparently in xdbg 3.0.1 (see https://twitter.com/derickr/status/1335544409555947520 and https://bugs.xdebug.org/bug_view_page.php?bug_id=00001903).

I guess that this means that a possible fix would be to either:

• add an if defined to the code,
• or mark this package incompatible with xdebug 3.0.0 in composer.json