Request For Review: JDK-8004832 Add new doclint package

[Jonathan Gibbons]

We need to add a new package, com.sun.tools.doclint, for the upcoming 
new doclint feature described in JEP 105.

Please review the minor build-related changes for the old and new build 
system in the following webrevs

http://cr.openjdk.java.net/~jjg/8004832/jdk
http://cr.openjdk.java.net/~jjg/8004832/langtools

The code changes in the langtools repo are being reviewed separately.

-- Jon