belong to *_style BT, but should belong to erp5_core, because this
feature should work on all ERP5 instance regardless its style. So, move them from erp5_xhtml_style to here.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@26150 20353a03-c40f-0410-a6d1-a30d3c3de9de