bug#27442: Un-obsolete x-clipboard-yank, or provide analogous functional

[Constantine Kharlamov]

Emacs says: "x-clipboard-yank is obsolete since 25.1; use ‘clipboard-yank’ 
instead." The problem is that clipboard-yank doesn't work same way as 
x-clipboard-yank does.

x-clipboard-yank always uses clipboard content, which is exactly what I need. 
I.e. if I set (setq select-enable-clipboard nil) to not clutter my clipboard 
with kills, I only get content from the clipboard. (don't get me wrong, 
kill-ring is very cool, and I extensively use it in evil-mode. But I prefer to 
explicitly point when I want a content in the clipboard, which happens an order 
of magnitude rarer than usage of kill-ring).

clipboard-yank uses a kill-ring instead. So if I set (setq 
select-enable-clipboard nil), every usage of the function gives me a random 
text that may or may not be in the clipboard.