Default web pages to right-to-left

* eww.el (eww-mode): Most web pages are left-to-right, so make
that the default (bug#19801).

* shr.el (shr-tag-html): Respect "dir" attributes
(left-to-right, right-to-left).

Backport:

(cherry picked from commit 9e089ec8)

lisp/net/eww.el

@@ -713,7 +713,8 @@ the like."
   (setq-local desktop-save-buffer #'eww-desktop-misc-data)
   ;; multi-page isearch support
   (setq-local multi-isearch-next-buffer-function #'eww-isearch-next-buffer)
-  (setq truncate-lines t)
+  (setq truncate-lines t
+        bidi-paragraph-direction 'left-to-right)
   (buffer-disable-undo)
   (setq buffer-read-only t))
 

lisp/net/shr.el

@@ -1102,6 +1102,15 @@ ones, in case fg and bg are nil."
 
 ;;; Tag-specific rendering rules.
 
+(defun shr-tag-html (dom)
+  (let ((dir (dom-attr dom 'dir)))
+    (cond
+     ((equal dir "ltr")
+      (setq bidi-paragraph-direction 'left-to-right))
+     ((equal dir "rtl")
+      (setq bidi-paragraph-direction 'right-to-left))))
+  (shr-generic dom))
+
 (defun shr-tag-body (dom)
   (let* ((start (point))
 	 (fgcolor (or (dom-attr dom 'fgcolor) (dom-attr dom 'text)))