RFR: 8066000: Sjavac TaskListeners should not provide empty implementations

[Andreas Lundblad]

Hi compiler-dev,

Please review this (trivial) fix for JDK-8066000.

Description:
Since JDK-8059591 the sjavac TaskListeners do no longer need to override the 'started' method.

Link to web review:
http://cr.openjdk.java.net/~alundblad/8066000

Link to bug reports:
http://bugs.openjdk.java.net/browse/JDK-8066000

-- Andreas Lundblad