avro

AVRO-463. C: Error messages

This patch adds a new avro_strerror() function, which returns a string
describing the most recent Avro error.  Every function that can return
an error code has been updated to provide an error string.  In
particular, the avro_schema_from_json function now fills in the Avro
error string with any parse errors that result from an invalid JSON
string.


git-svn-id: https://svn.apache.org/repos/asf/avro/trunk@1074608 13f79535-47bb-0310-9956-ffa450edef68