Unexpected behavior with respond_to

Hi Svilen,

FYI:

https://rails.lighthouseapp.com/projects/8994/tickets/5277-rails-300rc-responds-strangely-to-empty-accept-header
https://rails.lighthouseapp.com/projects/8994/tickets/5278-order-of-an-accept-header-should-not-matter-to-respond_to-rails-300rc

I believe that rails is doing the wrong thing here, but I do not have
time to supply a patch.

best, Erik Hetzner