'Get quota' function

Hello,

The _quota_by_role_fetch_count() and quota_by_role_user() are fine but I needed another function to get the list of quota and the associated limit and posts left. This function can be used anywhere in order to get and display the quota in some other formats and not only on the user account page.

I have attached a patch that provides this quota_by_role_get_quota() function. I have updated the code so that quota_by_role_user() use it.

Ah, the patch also fix #369134: Forever quota is shown wrong in user profile.

Cheers