RFR: JDK-8238646 Cleanup signature and use of CommentHelper

[Jonathan Gibbons]

Please review a moderately simply change to cleanup the use of 
CommentHelper.  (It's a non-goal to change the functionality of 
CommentHelper at this time.)

CommentHelper objects are given a reference to the BaseConfiguration 
when they are constructed, but this is ignored. Subsequently, many 
methods that need access to the configuration require the configuration 
to be passed in as a parameter.

By saving the value passed in to the constructor, we can remove the need 
for the parameter for the various CommentHelper methods.

The primary changes are to the signatures of the methods in 
CommentHelper, removing the need for an additional configuration 
parameter. This affects the use sites of those metods, but the change is 
just to drop the now-unnecessary parameter.

I also simplified the lambda expressions in CommentHelper, so that the 
file is now free of IDE warnings.  I stopped short of fixing names like 
"dtree" and "rtree" to pass the spelling checker.

-- Jon

JBS: https://bugs.openjdk.java.net/browse/JDK-8238646
Webrev: http://cr.openjdk.java.net/~jjg/8238646/webrev/