Allow plugins to hide the "Additional Capabilities" output on the profile / user edit page

[jamescollins]

If a plugin adds an individual capability to one or more user accounts, their profile page automatically displays an "Additional Capabilities" section.

This information is also displayed when editing another user account.

This functionality was added in [2872].

I think this output should be optional, as it may confuse the end user.

I propose adding a simple filter that will allow plugins to override this.

[jamescollins]

Corrected patch against r10485

[jamescollins]

Improved patch against r10642

[jamescollins]

I have updated the simple patch against r10642.

As far as I can tell, the attached patch doesn't change any existing behaviour(s), so I'd like to see this patch included in WP 2.8 if possible.

Thanks.

[westi]

(In [10645]) Allow a plugin to hide the extra capabilities listing on profiles. Fixes #9024 props jamescollins.