Clean up:

- domain.com => example.com, as suggested by RFC 2606
- fix and introduce more dockbook tags
- fix white spaces and use CDATA sections
- add some paras to make the text more reader friendly

docs/en/designers/language-variables/language-variables-smarty.xml

@@ -18,7 +18,7 @@
       <title>displaying request variables</title>
       <programlisting>
 <![CDATA[
-{* display value of page from URL (GET) http://www.domain.com/index.php?page=foo *}
+{* display value of page from URL (GET) http://www.example.com/index.php?page=foo *}
 {$smarty.get.page}
 
 {* display the variable "page" from a form (POST) *}