Fix bad skip of sstables on slice query with composite start/finish

Patch by Tyler Hobbs; reviewed by Sylvain Lebresne for CASSANDRA-6825
Fix unintended update with conditional statement

patch by slebresne; reviewed by iamaleksey for CASSANDRA-6893
Replace equals by type compare
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	src/java/org/apache/cassandra/cql3/statements/SelectStatement.java
	src/java/org/apache/cassandra/db/marshal/CompositeType.java
	test/unit/org/apache/cassandra/db/marshal/CompositeTypeTest.java
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	src/java/org/apache/cassandra/cql3/ColumnCondition.java