JDK 8 code review request for 7140820 Add covariant overrides to Collections clone methods

[Joe Darcy]

Hello,

As an indirect outgrowth of warnings cleanup day, various categories of 
warnings can be eliminated by in the use of Cloneable types by 
overriding the

     Object clone()

method inherited from java.lang.Object with a covariant override such as

     MyType clone()

Please review my changes for

     7140820 Add covariant overrides to Collections clone methods
     http://cr.openjdk.java.net/~darcy/7140820.0/

which add such covariant override clone methods to collections and a few 
other classes in java.util.  Doing a full JDK build with these changes, 
I've also made alterations to other classes to remove now superfuous 
casts (casts which are a javac lint warning!) and some unneeded 
@SuppressWarnings annotations.  I also cleaned up a few rawtypes 
warnings while in editing files in java.util.

(Note that the old specListeners method in EventRequestSpecList.java was 
much buggy; it cast an ArrayList from runtime.specListeners to a Vector.)

Thanks,

-Joe