Handle CQL3 SELECT duplicate IN restrictions on clustering columns

patch by Aleksey Yeschenko; reviewed by Jonathan Ellis for
CASSANDRA-5856
Merge branch 'cassandra-1.2' into cassandra-2.0.0

Conflicts:
	CHANGES.txt
	src/java/org/apache/cassandra/cql3/statements/SelectStatement.java
Merge branch 'cassandra-2.0.0' into cassandra-2.0