Strip non utf8 content when displaying diff (ruby1.9 compatibility).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@4604 e93f8b46-1217-0410-a6f0-8f06a7374b81

test/fixtures/files/060719210727_changeset_utf8.diff

@@ -0,0 +1,13 @@
+Index: trunk/app/controllers/issues_controller.rb
+===================================================================
+--- trunk/app/controllers/issues_controller.rb	(révision 1483)
++++ trunk/app/controllers/issues_controller.rb	(révision 1484)
+@@ -149,7 +149,7 @@
+         attach_files(@issue, params[:attachments])
+         flash[:notice] = 'Demande créée avec succès'
+         Mailer.deliver_issue_add(@issue) if Setting.notified_events.include?('issue_added')
+-        redirect_to :controller => 'issues', :action => 'show', :id => @issue,  :project_id => @project
++        redirect_to :controller => 'issues', :action => 'show', :id => @issue
+         return
+       end		
+     end