HIVE-1466: Add NULL DEFINED AS to ROW FORMAT specification
Review Request #16207 - Created Dec. 12, 2013 and updated
Support configurable null format for tables and writing out to directory. Using a non-default null format is a bit while creating a table, and pretty much impossible to export the data to local filesystem using insert overwrite directory. The patch enhances the SQL syntax to support 'NULL DEFINED AS' construct for create table as well as insert overwrite directory.
Added new tests.