Improve precision pixel scrolling

Improve precision pixel scrolling

* lisp/pixel-scroll.el (pixel-scroll-precision-scroll-down-page)
(pixel-scroll-precision-scroll-up-page): Use
pos-visible-in-window-p to opt between the next line or to the
window start rather than computing the next position by hand.
(pixel-scroll-precision-mode): Disable
make-cursor-line-fully-visible.  (bug#65214)
* src/image.c (jpeg_load_body): Fix crash if libjpeg detects an
error before ximg is initialized.
* src/xdisp.c (display_and_set_cursor): Don't display cursor in
vscrolled-away row.