Correctly handle limits in CompositesSearcher

patch by Aleksey Yeschenko; reviewed by Sylvain Lebresne for
CASSANDRA-5975
Merge branch 'cassandra-1.2' into cassandra-2.0

Conflicts:
	CHANGES.txt
	src/java/org/apache/cassandra/db/index/composites/CompositesSearcher.java
Fix merge (s/>/>= in CompositesSearcher)