Make shr fold long title texts

* net/shr.el (shr-fold-text): New function.
(shr-show-alt-text, shr-urlify, shr-tag-img): Use it to fold long
alt/title texts.
(shr-fold-text): Inhibit state from being altered.
isearch-open-necessary-overlays: Open overlay ending at point

* lisp/isearch.el (isearch-open-necessary-overlays): Open overlay
ending at point (bug#19333).