AVRO-1241. Java: Optimize Trevni string input.  Contributed by Joseph Adler.

git-svn-id: https://svn.apache.org/repos/asf/avro/trunk@1442391 13f79535-47bb-0310-9956-ffa450edef68
AVRO-1228. Java: Fix Trevni to use default values for missing Avro fields.

git-svn-id: https://svn.apache.org/repos/asf/avro/trunk@1442398 13f79535-47bb-0310-9956-ffa450edef68