[BUGFIX] Cannot auto-load SC_* classes

These script files cannot be auto-loaded because they also include
runnable code.

Resolves: #53075
Releases: 4.7, 4.5
Change-Id: Ib3a956b69355466016099e996b6ca6c5f89978cd
Reviewed-on: https://review.typo3.org/24979
Reviewed-by: Ernesto Baschny
Tested-by: Ernesto Baschny