GitLab

* doc/emacs/frames.texi (Mouse Commands): Document mouse-yank-primary.

* doc/emacs/killing.texi (Primary Selection): Document `only' setting for
select-active-regions.

* doc/emacs/mark.texi (Setting Mark): Reference Shift Selection node.

* doc/lispref/frames.texi (Window System Selections): Discussion of
x-select-enable-clipboard moved to Emacs manual.