Handle negative timestamps in writetime method

patch by slebresne; reviewed by thobbs for CASSANDRA-8139
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	CHANGES.txt
	src/java/org/apache/cassandra/cql3/UpdateParameters.java
Merge branch 'cassandra-2.1' into trunk

Conflicts:
	src/java/org/apache/cassandra/cql3/statements/Selection.java
Fix race in RecoveryManagerTest
patch by Sam Tunnicliffe; reviewed by jbellis for CASSANDRA-8176
merge from 2.1
Update CQLSSTableWriter to allow parallel writing of SSTables on the same table within the same JVM

Patch by Carl Yeksigian, reviewed by Benjamin Lerer for CASSANDRA-7463
Merge branch 'cassandra-2.0' into cassandra-2.1
Merge branch 'cassandra-2.1' into trunk
Fix totalDiskSpaceUsed calculation

patch by yukim; reviewed by krummas for CASSANDRA-8205
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	CHANGES.txt
	src/java/org/apache/cassandra/io/sstable/SSTableDeletingTask.java
Merge branch 'cassandra-2.1' into trunk
cqlsh: upgrade bundled python driver to 2.1.2

Patch by Tyler Hobbs for CASSANDRA-8031
Merge branch 'cassandra-2.1' into trunk
Fix merge on test
Merge branch 'cassandra-2.1' into trunk
fix test, take 2
Merge branch 'cassandra-2.1' into trunk
add jmxPort to stress args (ninja)
Merge branch 'cassandra-2.1' into trunk
Update CQLSSTableWriter to allow parallel writing of SSTables on the same table within the same JVM

Patch by Carl Yeksigian, reviewed by Benjamin Lerer for CASSANDRA-7463