fix build
Merge branch 'cassandra-1.2' into cassandra-2.0
Update sstablesPerReadHistogram to use biased sampling
patch by jbellis; reviewed by yukim for CASSANDRA-6164
add live/tombstoned histogram counts to cfstats
patch by Mikhail Stepura; reviewed by jbellis for CASSANDRA-5889
merge from 1.2
Merge branch 'cassandra-2.0' into trunk