bug#46621: Copy line

[Juri Linkov]

>> But there is no one-key binding for this command.
>
> People may bind it to whatever they choose, like `H-c', if they like the
> command.

Why would one want to sacrifice a short keybinding when
it's easier to use a keybinding of any length to copy the
current line, then use C-y C-y C-y ...  Also it solves
the main discrepancy of this feature request - whether
to keep point unmoved or to move it on the copied line:
C-y supports the prefix arg `C-u C-y', problem solved.