[TASK] Remove class.* from /typo3/

Removes last few class file wrappers from /typo3/ folder.
Those files were renamed and moved during namespacing.

Few references are adapted in comments only.
- Please also see removed require_once statement.

Change-Id: I25a33aea5adde12ce1bca35e1473ccc1d6ed41b0
Resolves: #48942
Releases: 6.2
Reviewed-on: https://review.typo3.org/21284
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring