PIG-3345: Handle null in DateTime functions (rohini)

git-svn-id: https://svn.apache.org/repos/asf/pig/trunk@1489439 13f79535-47bb-0310-9956-ffa450edef68
PIG-3342: Allow conditions in case statement (cheolsoo)


git-svn-id: https://svn.apache.org/repos/asf/pig/trunk@1489491 13f79535-47bb-0310-9956-ffa450edef68
PIG-3280: Document IN operator and CASE expression (cheolsoo)


git-svn-id: https://svn.apache.org/repos/asf/pig/trunk@1489580 13f79535-47bb-0310-9956-ffa450edef68