[PATCH] ActiveSupport::OrderedHash#update Does Not Set Keys

Using update on an ActiveSupport::OrderedHash does not set keys correctly meaning that it cannot be iterated over with each, etc.

For example:

hash = ActiveSupport::OrderedHash.new
hash.update(:name => "Bob")
# => #<OrderedHash {:name=>"Bob"}>
hash.keys
# => []
hash.each do |key, value|
  puts value
end
# => []

This can be fixed by aliasing update to merge! as is done in Rubinius' Hash implementation (c.f. http://github.com/evanphx/rubinius/blob/master/kernel/common/hash.r... ).

Please find attached a patch and test case to resolve this issue.