[FIX]cleditor: richtext box does not work into IE11 , code backported from odoo 8.0 (Maintenance Case: 614826)

Hello,

Steps to reproduce this issue:
Reproduce only into IE11 in windows OS for OpenERP version 7. Checked on runbot.
1.  Navigate Menu Knowledge -> Pages -> Pages 
3.  Try to edit some content into the rich text box(html widget) ,As soon as we save the text, it disappear and seems not saved.

Proposed branch fixes this issue.