Fix paging bug with deleted columns

patch by slebresne; reviewed by iamaleksey for CASSANDRA-6748
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	src/java/org/apache/cassandra/service/pager/AbstractQueryPager.java
Merge branch 'cassandra-2.1' into trunk
Fix unit test post-merge
Merge branch 'cassandra-2.1' into trunk