Some tiny patches for review

Just going through some of my old patches and hoping to get them
reviewed/committed - all tiny house-keeping patches. Anyway, here
goes:

http://dev.rubyonrails.org/ticket/10895 - Add missing tests for
AR::B#to_json for more than 1 :include. I had someone ask me about how
fumbled myself on the syntax. This extra test should clarify.
http://dev.rubyonrails.org/ticket/10822 - Document Module/
Class#cattr_* extensions and remove unnecessary #flatten. Cleaned up
the tests a bit as well.
http://dev.rubyonrails.org/ticket/10809 -
asset_tag_helper#compute_asset_host shouldn't bail in Ruby's verbose
or warning mode (-v/-w).

Thanks!

Cheers,
Chu Yeow