Ninja-unify 1.1/1.2/2.0 system tests
fix 2i updates with indentical values and timestamps
patch by Sam Tunnicliffe; reviewed by jbellis for CASSANDRA-5540
merge from 1.2
use ImmutableSet instead of unmodifiableSet
enable native protocol by default
Merge branch 'cassandra-1.2' into trunk
add 3997 to CHANGES
Move CassandraServerTest.test_get_count() to thrift server tests
Merge branch 'cassandra-1.1' into cassandra-1.2

Conflicts:
	test/unit/org/apache/cassandra/service/CassandraServerTest.java
Merge branch 'cassandra-1.2' into trunk

Conflicts:
	test/unit/org/apache/cassandra/service/CassandraServerTest.java
avoid NPE on describe cf with no compaction strategy (local)
Merge branch 'cassandra-1.2' into trunk
Fix intersection with Bound computation

patch by wy96f; reviewed by slebresne for CASSANDRA-5551
Merge branch 'cassandra-1.2' into trunk
Backport #5551 to 1.1
Merge branch 'cassandra-1.1' into cassandra-1.2
Fix changelog
Merge branch 'cassandra-1.2' into trunk
replace Thread.sleep with Uninterruptibles.sleepUninterruptibly
patch by Mikhail Mazursky; reviewed by jbellis for CASSANDRA-5557
add nodetool enablebackup/disablebackup
patch by pmargolin reviewed by dbrosius for CASSANDRA-5556