RFR: [simple,docs] JDK-8223654: Clean up @jls references in com.sun.source

[Jonathan Gibbons]

Please review a simple update to the `@jls` tags in the docs for classes 
in the com.sun.source.tree API, to being them into stylistic consistency 
with other uses of `@jls` and `@jvms` elsewhere in the JDK docs. This 
will facilitate checking these tags for accuracy, and/or linking to the 
relevant sections of the specs.

There's no semantic change here, so no CSR.

-- Jon


JBS: https://bugs.openjdk.java.net/browse/JDK-8223654
Webrev: http://cr.openjdk.java.net/~jjg/8223654/webrev.00/