Don't drop local mutations without a trace

patch by Aleksey Yeschenko; reviewed by Jonathan Ellis for
CASSANDRA-6510
Merge branch 'cassandra-1.2' into cassandra-2.0

Conflicts:
	CHANGES.txt
Merge branch 'cassandra-2.0' into trunk
Ninja fix typo
Don't allow null max_hint_window_in_ms
patch by Nate McCall; reviewed by jbellis for CASSANDRA-6419
merge from 1.2
Merge branch 'cassandra-2.0' into trunk
remove dead code
simplify use of columnType, used only for super column types
use StringBuilder correctly
Fix potential assertion error in AbstractQueryPager.discardFirst

patch by slebresne; reviewed by iamaleksey for CASSANDRA-6447
Merge branch 'cassandra-2.0' into trunk
Fix tests
Merge branch 'cassandra-2.0' into trunk
UserType注释
Merge branch 'trunk' of http://git-wip-us.apache.org/repos/asf/cassandra into trunk