Issue #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits

Issue #2563803 by borisson_, DietrichM: Remove deprecated functions from core/modules/system/tests/modules/module_test/module_test.module

Issue #2363139 by Wim Leers, dawehner, larowlan: _content controllers may only return render arrays, not strings.