erp5_web: generate valid html

<u> tag does not exist in the standard used by erp5_web; use something which
should be equivalent

bt5/erp5_web/SkinTemplateItem/portal_skins/erp5_web_minimal_theme/language_selector.xml

@@ -40,7 +40,7 @@
                        available_language_list here/getAvailableLanguageList;\n
                        absolute_url here/absolute_url">\n
 <tal:block tal:repeat="language language_list" tal:condition="python:len(available_language_list) > 1">\n
-<b tal:condition="language/selected"><u tal:content="language/id"/></b>\n
+<b tal:condition="language/selected"><span style="text-decoration: underline" tal:content="language/id"/></b>\n
 <a tal:attributes="href python:\'%s/Base_doLanguage?select_language=%s\' % (absolute_url, language[\'id\'])"\n
    tal:content="language/id" tal:condition="python: language[\'id\'] in available_language_list and not language.get(\'selected\')"/>\n
 </tal:block>\n

bt5/erp5_web/bt/revision

-1102
+1103
\ No newline at end of file