TYPO3 Core

Fix it so the fixAttrib.[attribute].list when used with 'class' handles multiple classes correctly.

Example, its not possible to have it work correctly when :
class="htmlarea-table greentable"
it doesn't pick up the greentable class.

So if it was set as fixAttrib.class.list=greentable,redtable,bluetable,normaltable,lgtable
and it then encountered class="greentable lgtable msoCrud" it should simply remove the msoCrud class and leave the rest.

(issue imported from #M11552)