Fix PRSI handling of CQL3 row markers for row cleanup

patch by Berenguer Blasi; reviewed by Aleksey Yeschenko for
CASSANDRA-7787
Merge branch 'cassandra-2.0' into cassandra-2.1.0

Conflicts:
	CHANGES.txt
	src/java/org/apache/cassandra/db/index/SecondaryIndexManager.java