(Thrift) fix range deletion of supercolumns

patch by Aleksey Yeschenko; reviewed by Sylvain Lebresne for
CASSANDRA-7733
Merge branch 'cassandra-2.0' into cassandra-2.1.0

Conflicts:
	CHANGES.txt
	src/java/org/apache/cassandra/thrift/CassandraServer.java
Merge branch 'cassandra-2.1.0' into cassandra-2.1