Ask for confirmation when a non-admin users tries to remove himself from a project (#4402).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@3249 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/member.rb

@@ -57,6 +57,14 @@ class Member < ActiveRecord::Base
     member_roles.detect {|mr| mr.inherited_from}.nil?
   end
   
+  def include?(user)
+    if principal.is_a?(Group)
+      !user.nil? && user.groups.include?(principal)
+    else
+      self.user == user
+    end
+  end
+  
   def before_destroy
     if user
       # remove category based auto assignments for this member