8080353: JShell: Better error message on attempting to add default method
Summary: Special handling for errors with "default" modifier
Reviewed-by: jlahoda
/build/
/dist/
/.idea/
nbproject/private/
/webrev
/.src-rev
/.jib/
.DS_Store
.metadata/
.recommenders/
test/nashorn/script/external
test/nashorn/lib
NashornProfile.txt
**/JTreport/**
**/JTwork/**