RFR [16] 8251550: Clean up jdk.javadoc and the related parts of jdk.compiler

[Pavel Rappo]

Hello,

Please review the below change for https://bugs.openjdk.java.net/browse/JDK-8251550

  http://cr.openjdk.java.net/~prappo/8251550/webrev.00/

This represents squashed commits that have accumulated in my git branch. Since the changeset has started to look dangerously big, I decided not to wait until we finish the migration to Git and GitHub, and push it sooner. The less the others have to merge, the better.

-Pavel