Improve offheap memcpy performance

Patch by tjake; reviewed my jbellis for CASSANDRA-5884
Merge branch 'cassandra-2.0' into trunk
make sure to release recently added CF metric
make sure to release recently added CF metric
Merge branch 'cassandra-1.2' into cassandra-2.0.0
Merge branch 'cassandra-2.0.0' into cassandra-2.0
Merge branch 'cassandra-2.0' into trunk

Conflicts:
	src/java/org/apache/cassandra/metrics/ColumnFamilyMetrics.java
Migrate key_alias->key_aliases on every schema migration (1.2)

Another follow-up to 5800
Merge branch 'cassandra-1.2' into cassandra-2.0.0
Merge branch 'cassandra-2.0.0' into cassandra-2.0
Added lines for BATCH response to v2 spec
Merge branch 'cassandra-2.0.0' into cassandra-2.0
Merge branch 'cassandra-2.0' into trunk