8185694: Replace SystemDictionaryShared::_java_platform_loader with SystemDictionary::is_platform_class_loader() Summary: added the creation of _java_platform_loader Reviewed-by: iklam, coleenp, mchung, dholmes, jiangli

^build/
^dist/
^.idea/
nbproject/private/
^webrev
^.src-rev$
^.jib/
\.DS_Store
\.metadata/
\.recommenders/
test/nashorn/script/external
test/nashorn/lib
NashornProfile.txt