TYPO3 Core

Problem:
If an extension is installed during a request, the autoloader cache must be removed.
If not, it may be that classes are not found because they are missing in the autoloader registry

Solution:
Remove the autoloader cache if t3lib_extmgm::removeCacheFiles() is called

Steps to reproduce:
Use a plain dummy package.
Call the 123 install wizard.
You'll get "PHP Fatal error: Class 'tx_dbal_querycache' not found", because dbal activates itself, but the caches are not flushed and 'tx_dbal_querycache' is not present in the autoloader registry.