* lisp/xt-mouse.el: Add mouse-tracking support.

* lisp/xt-mouse.el: Add mouse-tracking support.

Fixes: debbugs:19416
* lisp/xt-mouse.el: Add mouse-tracking support.
(xterm-mouse-translate-1): Handle mouse-movement events.
(xterm-mouse--read-event-sequence-1000)
(xterm-mouse--read-event-sequence-1006): Delete functions.
(xterm-mouse--read-event-sequence): New function that handles both at
the same time.  Handle mouse-movements.
(xterm-mouse--read-utf8-char, xterm-mouse--read-number-from-terminal):
New functions.
(xterm-mouse-event): Simplify.
(xterm-mouse-tracking-enable-sequence)
(xterm-mouse-tracking-disable-sequence): Enable mouse tracking.

* lisp/mouse.el (mouse-drag-line): Also ignore `vertical-line' prefix events.