This patch fixes the unexceptional exceptions ecountered in FastCharStream and SupportClass

The java version of Lucene handles end-of-file in FastCharStream by throwing an exception. This behavior has been ported to .NET but the behavior carries an unacceptable cost in the .NET environment. This patch is based on the prior work in LUCENENET-8 and LUCENENET-11, which I gratefully acknowledge for the solution. While I understand that this patch is outside of the current project specification in that it deviates from the "pure" nature of the port, I believe that it is very important to make the patch available to any developer looking to leverage Lucene.Net in their project. Thanks for your consideration.