Fixing Plugin and Mailer default_url_options.

Both the plugin hooks and Mailer were setting default_url_options incorrectly
and causing ActionContoller::UrlWritter to cache the settings on the module
(mattr_accessor) causing several url generators to fail in either the plugin
hooks or the Mailer.

* Replaced Mailer's use of the default_url_options accessor with the proper class method
* Replaced Hook's use of the default_url_options accessor with the proper class method on the ViewListener class
* Added a test to reproduce the bugs in the Mailer when a hook is registered (thanks Chaoqun Zou)

  #2542

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@2522 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/mailer.rb

@@ -23,6 +23,12 @@ class Mailer < ActionMailer::Base
   include ActionController::UrlWriter
   include Redmine::I18n
 
+  def self.default_url_options
+    h = Setting.host_name
+    h = h.to_s.gsub(%r{\/.*$}, '') unless Redmine::Utils.relative_url_root.blank?
+    { :host => h, :protocol => Setting.protocol }
+  end
+  
   def issue_add(issue)
     redmine_headers 'Project' => issue.project.identifier,
                     'Issue-Id' => issue.id,
@@ -213,12 +219,6 @@ class Mailer < ActionMailer::Base
     set_language_if_valid Setting.default_language
     from Setting.mail_from
     
-    # URL options
-    h = Setting.host_name
-    h = h.to_s.gsub(%r{\/.*$}, '') unless Redmine::Utils.relative_url_root.blank?
-    default_url_options[:host] = h
-    default_url_options[:protocol] = Setting.protocol
-    
     # Common headers
     headers 'X-Mailer' => 'Redmine',
             'X-Redmine-Host' => Setting.host_name,