Code cleanup on KStemmer [LUCENE-5358]

This affects all versions with KStemmer in them

The code of KStemmer needs some intensive cleanup, just to give you some idea on something that immediately popped up:

https://github.com/apache/lucene-solr/blob/trunk/lucene/analysis/common/src/java/org/apache/lucene/analysis/en/KStemmer.java#L283-286

I'll be happy to do this myself, just wanted to check in advance to see if this is something you'd consider accepting in

---
Migrated from [LUCENE-5358](https://issues.apache.org/jira/browse/LUCENE-5358) by Itamar Syn-Hershko

Start with lucene/analysis/common/src/java/org/apache/lucene/analysis/en/KStemmer.java, especially the linked lines 283-286, and review the surrounding implementation. The issue does not define specific cleanup tasks or completion criteria, so establish those before changing code.

Written by the indexing model from the issue text.