[master] accept >4g max-{,a}cache-size

[master] accept >4g max-{,a}cache-size

3506.	[func]		When setting "max-cache-size" and "max-acache-size",
			the keyword "unlimited" is no longer defined as equal
			to 4 gigabytes (except on 32-bit platforms); it
			means literally unlimited. [RT #32358]

3505.	[bug]		When setting "max-cache-size" and "max-acache-size",
			larger values than 4 gigabytes could not be set
			explicitly, though larger sizes were available
			when setting cache size to 0. This has been
			corrected; the full range is now available.
			[RT #32358]