Implement caching of authorization results

Patch by Aleksey Yeschenko; reviewed by Jonathan Ellis for
CASSANDRA-4295
Merge branch 'cassandra-1.2' into trunk

Conflicts:
	CHANGES.txt
Add support for LZ4 compression
patch by Adrien Grand; reviewed by tjake for CASSANDRA-5038
Merge branch 'cassandra-1.2' into trunk
Remove duplicate 5038 from CHANGES.txt