shr: alt text truncation

[Katsumi Yamaoka <yamaoka@jpl.org>]

Currently the width of an alt text is limited by 8, so I come
across ones like the following occasionally:

+--------+
|Amazon.c|
+--------+
[   image   ]

Is it really necessary?  Even so, can't the limit be extended to
shr-width at least in a table?  For instance:

--- shr.el~	2010-11-04 22:03:07 +0000
+++ shr.el	2010-11-05 00:51:26 +0000
@@ -557,3 +557,6 @@
-	  (let ((shr-state 'space))
-	    (if (> (string-width alt) 8)
-		(shr-insert (truncate-string-to-width alt 8))
+	  (let ((shr-state 'space)
+		(limit (if (zerop shr-table-depth) 8 shr-width)))
+	    (if (> (string-width alt) limit)
+		(shr-insert
+		 (concat (truncate-string-to-width alt (- limit 3))
+			 (make-string 3 ?.)))