Fix a very serious bug reported by Apache Hive developers. This bug was only triggered when using nested generic types (e.g. Maps of Maps). Generic type parameters to be used for (de)serialization were not properly reset in case of referring to a previously used object.

git-svn-id: http://kryo.googlecode.com/svn/trunk@406 a9660ef0-a895-11de-8ba5-91705c1537ed