kill-region in 24.4 shouldn't require BEG and END

[Kelly Dean <kelly@prtime.org>]

If the REGION argument is non-nil, then BEG and END shouldn't be required, since they're unused (except in one place where they aren't needed). So the test
⌜unless (and beg end)⌝
in kill-region should be
⌜unless (or region (and beg end))⌝
and the docstring should point out that if REGION is non-nil, then BEG and END are unused and might as well be nil.

The one place in kill-region where BEG and END are unnecessarily used if REGION is non-nil is the line
⌜(kill-append string (< end beg))⌝
which should be something like
⌜(kill-append string (if region
			(< (point) (mark))
		       (< end beg)))⌝
and similarly for copy-region-as-kill.

Without these changes, both kill-region and its docstring are confusing.

Also, it would be clearer to have different names for the region between the cursor (er. point) and mark vs. a region between two specified positions; maybe call the latter a ‟range”, and have a cut-range function that takes BEG and END and have a cut-region function that takes no arguments, have both call kill-region, rename the latter to ‟cut-range-or-region”, and provide ‟kill-region” as an alias to the latter and mark it as deprecated, but I guess we'd have to wait 20 years before that alias could be safely removed. To go along with that, rename the kill-ring to ‟clip-ring” (not ‟cut-ring” since it holds not just cut things, but also copied things) to be memorable as a ring of clippings since everybody knows what a clipboard is, and rename all the associated functions.
But Emacs just wouldn't be the same if it didn't let us kill things anymore. Maybe the traditional, weaponized version is better after all.