Get controller/layout_test.rb running on new base except for ActionController::Base.exempt_from_layout which is going to be deprecated.

Cleaned up the #render_to_body chain by extracting determining the templates to render to a separate hook point.

Ruby 1.9 compat: don't rely on lexical scoping since the included block is called from dependency_module

[#2686 state:committed]
Signed-off-by: NJeremy Kemper <jeremy@bitsweat.net>

Single-require forward compatibility with new Ruby features like Object#tap, Enumerable#group_by, and Process.daemon. Code with the latest but run anywhere.