8011044: Remove support for 1.5 and earlier source and target options
Reviewed-by: darcy, jjg
Contributed-by: neil.toda@oracle.com, brian.goetz@oracle.com

6900037: javac should warn if earlier -source is used and bootclasspath not set
Reviewed-by: darcy

6968063: provide examples of code that generate diagnostics
Reviewed-by: mcimadamore