MDL-12815 - Quiz uses inconsistent class attribute for the paging bar.

I have added the standard .paging class, but I have left the old class there too, so as not to break existing themes.
MDL-12815 - Quiz uses inconsistent class attribute for the paging bar.

I have added the standard .paging class, but I have left the old class there too, so as not to break existing themes.

dilawar/moodle