hg: jigsaw/jake/langtools: Add missing comments

[jonathan.gibbons at oracle.com]

Changeset: 806170c571fc
Author:    jjg
Date:      2016-03-08 14:35 -0800
URL:       http://hg.openjdk.java.net/jigsaw/jake/langtools/rev/806170c571fc

Add missing comments

! src/jdk.compiler/share/classes/com/sun/source/tree/ExportsTree.java
! src/jdk.compiler/share/classes/com/sun/source/tree/ModuleTree.java
! src/jdk.compiler/share/classes/com/sun/source/tree/ProvidesTree.java
! src/jdk.compiler/share/classes/com/sun/source/tree/RequiresTree.java
! src/jdk.compiler/share/classes/com/sun/source/tree/TreeVisitor.java
! src/jdk.compiler/share/classes/com/sun/source/tree/UsesTree.java