Sets a upper limit on how far into the the file a Range request
	may be to cause Squid to prefetch the whole file. If beyond this
	limit Squid forwards the Range request as it is and the result
	is NOT cached.

	This is to stop a far ahead range request (lets say start at 17MB)
	from making Squid fetch the whole object up to that point before
	sending anything to the client.

	A value of -1 causes Squid to always fetch the object from the
	beginning so it may cache the result. (2.0 style)

	A value of 0 causes Squid to never fetch more than the
	client requested. (default)