* lisp/mouse.el (mouse-drag-line): Use set-transient-map.
(mouse--down-1-maybe-follows-link): Remove unused var `this-event'.
(mouse-yank-secondary): Use gui-get-selection.
(mouse--down-1-maybe-follows-link): Use read-key.

* lisp/subr.el (read-key): Fix clicks on the mode-line.
(set-transient-map): Return exit function.

* lisp/xt-mouse.el: Add `event-kind' property on the fly from
xterm-mouse-translate-1 rather than statically at the outset.