HIVE-4126 [jira] remove support for lead/lag UDFs outside of UDAF args
(Harish Butani via Ashutosh Chauhan)

Summary:
remove support for lead/lag UDFs outside of UDAF args

Select Expressions such as
p_size - lead(p_size,1)
are currently handled as non aggregation expressions done after all over clauses are evaluated.
Once we allow different partitions in a single select list(Jira 4041), these become ambiguous.

	the equivalent way to do such things is either to use lead/lag UDAFs with expressions ( support added with Jira 4081)
	stack windowing clauses with inline queries. select lead(r,1).. from (select rank() as r....)...

Test Plan: existing tests

Reviewers: JIRA, ashutoshc

Reviewed By: ashutoshc

Differential Revision: https://reviews.facebook.net/D9105

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/ptf-windowing@1454504 13f79535-47bb-0310-9956-ffa450edef68