update versioning for 2.1.0-rc4 release
Fix jvm version detection when JAVA_TOOL_OPTIONS in environment

Patch by Gregory Ramsperger, reviewed by brandonwilliams for
CASSANDRA-7572
Merge branch 'cassandra-2.0' into cassandra-2.1.0
Merge branch 'cassandra-2.1.0' into cassandra-2.1

Conflicts:
	CHANGES.txt