prototype rails.js fix for forms with multiple submit buttons

Hello,

Please see my ticket at
https://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/5356
for a fix for supporting multiple submit buttons in forms using the
prototype version of rails.js.

The ticket goes into more detail. Please let me know of any changes,
comments, etc. My javascript-fu is not as good as my ruby-fu.

Thanks