8205615: Start of release updates for JDK 12 8205621: Increment JDK version for JDK 12 8193292: Add SourceVersion.RELEASE_12 8193290: Add source 12 and target 12 to javac 8205619: Bump maximum recognized class file version to 56 for JDK 12 Reviewed-by: alanb, smarks, jjg, mr, erikj, psandoz, dholmes Contributed-by: erik.joelsson@oracle.com, mikael.vidstedt@oracle.com, joe.darcy@oracle.com