Fix skipping columns with multiple slices

patch by frousseau & slebresne; reviewed by frousseau & slebresne for CASSANDRA-6119
Merge branch 'cassandra-1.2' into cassandra-2.0

Conflicts:
	src/java/org/apache/cassandra/db/columniterator/IndexedSliceReader.java
Merge branch 'cassandra-2.0' into trunk
Fix test build
Merge branch 'cassandra-2.0' into trunk
Disallow empty column names in cql
patch by dbrosius reviewed by slebresne for cassandra-6136
add concurrent sets to progressByHost (CASSANDRA-6129)
Merge branch 'cassandra-2.0' into trunk
eliminate redundant classpath creation

Patch by eevans; reviewed by Anton Winter for CASSANDRA-6101
Merge cassandra-2.0 into trunk
cleanup
Merge branch 'cassandra-2.0' into trunk
fix assertionerror from #6132
cleanup
merge from 1.2
Merge remote-tracking branch 'origin/trunk' into trunk
Merge branch 'cassandra-2.0' into trunk
fix addCallback for XDC requests too
merge from 1.2
Merge branch 'cassandra-2.0' into trunk