title: Drupal 7 : How do I give permission access for an user with a defined role ?
body: <p>I have 2 roles: <em>administrator</em> and <em>webmaster</em>.
  I added diverse permissions in a module custom. Then in "admin/people/permissions" I authorize the access to a permission for a role.</p>
  
  <p>I would like authorize the access to a permission, not for a role, but for a user with a defined role.</p>
  
  <p>More exactly: I wish that the role <em>administrator</em> can authorize, or not, the access to a permission for each user with the role webmaster.</p>
  
  <p>Is there any module for achieving this ? </p>
  
  <p>How can I realise this ?</p>