lisp/ox-texinfo.el: Fix export of source blocks

* lisp/ox-texinfo.el (org-texinfo-src-block): Escape texinfo commands
  within source blocks to ensure proper export.  `@ { }' all need to
  be escaped to ensure proper formatting when processing to info.

lisp/ox-texinfo.el

@@ -1431,16 +1431,18 @@ as a communication channel."
 CONTENTS holds the contents of the item.  INFO is a plist holding
 contextual information."
   (let* ((lang (org-element-property :language src-block))
-	 (lisp-p (string-match-p "lisp" lang)))
+	 (lisp-p (string-match-p "lisp" lang))
+	 (src-contents (org-texinfo--sanitize-content
+		   (org-export-format-code-default src-block info))))
     (cond
      ;; Case 1.  Lisp Block
      (lisp-p
       (format "@lisp\n%s@end lisp"
-	      (org-export-format-code-default src-block info)))
+	      src-contents))
      ;; Case 2.  Other blocks
      (t
       (format "@example\n%s@end example"
-	      (org-export-format-code-default src-block info))))))
+	      src-contents)))))
 
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