8000269: Cleanup javadoc warnings

[Alan Bateman]

A small number of javadoc warnings have sneaked into the jdk8 builds 
lately. They are easily fixed but it's a good opportunity to try out 
Jon's doccheck tool [1], built on the DocTree API, and get a better 
workout. I decided to mostly focus on -Xmsgs:reference, which covers 
references like @param and @throws. I fixed a small number of html 
issues along the way but that was not my focus. The webrev, which fixes 
up most of the reference issues in roughly the core area, is here:

http://cr.openjdk.java.net/~alanb/8000269/webrev/index.html

When I say "most" then I excluded j.u.c and java.lang.invoke.

The reason that so many files are changed is because doccheck looks at 
private and package-private classes and methods that wouldn't normally 
be in the javadoc. Also, no foray into the *Permission classes is 
possible without fixing up at least a few formatting issues. Note that 
there is one non-javadoc change in this webrev; in java.net.Inet4Address 
I have removed a private static field that has not been used for several 
releases.

The changes are trivial and easy to review. At it covers many areas then 
partial reviews are okay too.

Thanks,

Alan.

[1] 
http://mail.openjdk.java.net/pipermail/compiler-dev/2012-September/004800.html