LUCENE-2372, LUCENE-2389 made it impossible to subclass core analyzers [LUCENE-3055]

#3448 and #3464 marked all analyzers as final. This makes ReusableAnalyzerBase useless, and makes it impossible to subclass e.g. StandardAnalyzer to make a small modification e.g. to tokenStream(). These issues don't indicate a new method of doing this. The issues don't give a reason except for design considerations, which seems a poor reason to make a backward-incompatible change

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Migrated from [LUCENE-3055](https://issues.apache.org/jira/browse/LUCENE-3055) by Ian Soboroff (@isoboroff), updated Sep 25 2011

Start by reviewing the analyzer changes referenced in #3448 and #3464, then inspect ReusableAnalyzerBase and the core analyzer classes to understand the compatibility impact. The issue does not name files or tests, and completion depends on deciding and validating a supported subclassing approach for analyzers such as StandardAnalyzer.

Written by the indexing model from the issue text.