Fix broken paging state with prepared statement

patch by slebresne; reviewed by thobbs for CASSANDRA-7120
Remove bogus validation post-6855
Fix IllegalArgumentException in CqlStorage

patch by slebresne; reviewed by driftx for CASSANDRA-7287
Fix broken paging state with prepared statement

patch by slebresne; reviewed by thobbs for CASSANDRA-7120
Merge branch 'cassandra-2.1' into trunk

Conflicts:
	CHANGES.txt