Add support for sound CAPTCHA with Internet Explorer 11

Preconditions: Open the XWiki instance in Internet Explorer 11 browser.

STEPS TO REPRODUCE:

1. Go to Administer Wiki
2. Click on Other > CAPTCHA
3. Select Type > Sound
4. Click on 'Save'
5. On the Sample CAPTCHA, click 'Listen'
6. Go to Users & Rights > Rights
7. Tick 'Require unregistered users to solve a CAPTCHA when posting a comment on a page'
8. Click on 'Users' and grant 'Comment' right to unregistered users
9. Log out of the wiki
10. Go to a page
11. Click in 'Comments' text box
12. Click on 'Listen'

EXPECTED RESULTS

The sound CAPTCHA can be heard when listening on it from the sample section on the Administration configuration page, as well as when posting a comment on a page when required.

ACTUAL RESULTS:

On IE11, the sound CAPTCHA does not work, nothing can be heard. Also, nothing happens if clicked on 'Reload'. No errors displayed in browser or console.