Add cqlsh help for auth statement

patch by iamaleksey; reviewed by slebresne for CASSANDRA-5233
Update debian version for 1.2.2 release
Fix pessimistic unit tests post-4671

Conflicts:
	test/unit/org/apache/cassandra/db/compaction/CompactionsPurgeTest.java
Merge branch 'cassandra-1.2' into trunk

Conflicts:
	test/unit/org/apache/cassandra/db/compaction/CompactionsPurgeTest.java