RFR: JDK-8041487: Fix proper dependencies for correct incremental build of javadocs

[Erik Joelsson]

(reposting with correct subject)

On 2014-04-22 15:28, Erik Joelsson wrote:
> I recently had to work with make/Javadoc.gmk and felt that it needed 
> some attention. This patch makes it behave correctly for incremental 
> builds and reduces the log output on the default log level to much 
> more manageable levels.
>
> I realize that we should probably rewrite this even more to reduce all 
> the code duplication, but choose to leave that for later.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8041487
> Webrev: http://cr.openjdk.java.net/~erikj/8041487/webrev.root.01/
>
> /Erik