AbstractMarshaller avoids SAXSource workaround when processExternalEntities=true

Issue: SPR-11737
SpringProperties falls back to ClassLoader.getSystemResource when loaded in bootstrap ClassLoader

Issue: SPR-11721
(cherry picked from commit 9cb5f48)
AnnotationTypeFilter prevents ASM-based loading of java.* and javax.* interfaces as well

Issue: SPR-11719
General defensiveness about the bootstrap ClassLoader (i.e. null ClassLoader)

Issue: SPR-11721
Polishing