bug#7077: 24.0.50; mouse-drag-copy-region - name should say copy as kill

[Drew Adams]

> > The name does not say anything about copying to the kill 
> > ring.  The name should, like `kill-ring-save' and
> > `copy-region-as-kill', say that this copies to the kill ring.
> >
> > Suggestion: `mouse-drag-copy-region-as-kill' or
> > `mouse-drag-kill-ring-save'.
> 
> I think that sounds reasonable, but, on the other hand, is it really
> necessary for all these functions to mention "kill" in the function
> name?  It seems intuitive (to me) that `mouse-drag-copy-region' puts
> stuff in the kill ring -- what else would it do?

1. "Copy" can mean a couple different things.  One misunderstanding might be to
copy the region to another location in a buffer - a la copy + paste.

2. It's helpful for Emacs to be consistent and put important Emacs terms into
command names that involve them.

In particular, this makes it easy to find them using things like `apropos'.
This principle is at least as old as the Unix `apropos' command and similar.  We
generally try to have Emacs commands that deal with buffer use `buffer' in the
name; those that deal with files use `file'; with yanking use `yank', etc.

It is not so obvious, especially to a newbie, that `mouse-drag-copy-region'
copies to the `kill-ring'.  Especially now that there are multiple copy-target
thingies such as the clipboard, paste buffer, interprogram XYZ, etc. (I don't
know the correct names).

In the beginning Emacs had only the `kill-ring' for copying and pasting, but
even in that context it would be helpful for a command such as this to have a
name similar to `kill-ring-save' and `copy-region-as-kill', suggesting that it
copies to the kill ring.