Change javac source and target default to 9

Summary

Change the default -source and -target value used by javac to 9.

Problem

As any new language feature are being implemented in JDK 9, the default source and target for javac should change to 9.  This is analogous to the source/target policy used in JDK 7 and JDK 8.

Solution

Change the defaults to source and target 9.

Specification

In the javac man page state the default source level is 9 and the default target is 9.