TYPO3 Core

In RTEhtmlarea there's a possibility to define custom links, e.g. by using a link handler. It might happen, that the name of the linkhandler (defined in $TYPO3_CONF_VARS['SC_OPTIONS']['tslib/class.tslib_content.php']['typolinkLinkHandler']) is different to the used link prefix (e.g. "linkhandler" vs. "myOwnLinkhandler:"). Furthermore it can happen that those custom links are not defined using a linkhandler at all.
Links that could not be validated by the current strict mechanism are shown as invalid in RTEhtmlarea.

The solution is to integrate a new hook that can take care of that validation in general.

(issue imported from #M10872)