Fix batchlog to account for CF truncation records

patch by Aleksey Yeschenko; reviewed by Jonathan Ellis for
CASSANDRA-6999
Merge branch 'cassandra-1.2' into cassandra-2.0

Conflicts:
	src/java/org/apache/cassandra/db/BatchlogManager.java
	src/java/org/apache/cassandra/db/ColumnFamilyStore.java
	src/java/org/apache/cassandra/db/HintedHandOffManager.java
	src/java/org/apache/cassandra/db/RowMutation.java
	src/java/org/apache/cassandra/db/commitlog/CommitLogReplayer.java
	src/java/org/apache/cassandra/service/StorageProxy.java
	test/unit/org/apache/cassandra/db/BatchlogManagerTest.java
	test/unit/org/apache/cassandra/db/HintedHandOffTest.java