Warning on leaving a page with unsaved content in textarea (#2910).

The warning can be turned off in the user's preference.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@4900 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/views/users/_preferences.html.erb

@@ -2,5 +2,6 @@
 <p><%= pref_fields.check_box :hide_mail %></p>
 <p><%= pref_fields.select :time_zone, ActiveSupport::TimeZone.all.collect {|z| [ z.to_s, z.name ]}, :include_blank => true %></p>
 <p><%= pref_fields.select :comments_sorting, [[l(:label_chronological_order), 'asc'], [l(:label_reverse_chronological_order), 'desc']] %></p>
+<p><%= pref_fields.check_box :warn_on_leaving_unsaved %></p>
 <% end %>