Prevent memory exhausted due to repeat appending "</table>"

Bug-Debian: #23 [CVE-2016-9633]
Origin: https://anonscm.debian.org/cgit/collab-maint/w3m.git/commit/?id=216722ed7282cec4338b177ea9ffdd39ad1b8c8c

file.c

@@ -6988,9 +6988,12 @@ completeHTMLstream(struct html_feed_environ *h_env, struct readbuffer *obuf)
 	obuf->table_level = MAX_TABLE - 1;
 
     while (obuf->table_level >= 0) {
+	int tmp = obuf->table_level;
 	table_mode[obuf->table_level].pre_mode
 	    &= ~(TBLM_SCRIPT | TBLM_STYLE | TBLM_PLAIN);
 	HTMLlineproc1("</table>", h_env);
+	if (obuf->table_level >= tmp)
+	    break;
     }
 }