Author: Paul Holden
MDL-69448 backup: fix capability checks when unable to copy user data.
When a given user doesn't have the capability to "Include user data"
during course copying, freeze the form element rather than not adding
it at all.
This caused problems as the element was required before preceding with
the course copy.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=404eabc7b5645af347e93dc58a2305b2de02a3b6
http://github.com/moodle/moodle/commit/404eabc7b5645af347e93dc58a2305b2de02a3b6
+ 4.0 en [copyfieldnotfound,core_backup]