[PATCH] ActiveSupport::OrderedHash#each* methods without block are incorrect in 1.8

In ruby 1.8.x, ordered hashes don't behave like normal hashes when calling each* methods without a block:

>> {:a => 1}.each
=> #<Enumerable::Enumerator:0x25637c>
>> h = ActiveSupport::OrderedHash.new.merge :a => 1
=> #<OrderedHash {:a=>1}>
>> h.each
LocalJumpError: no block given
    ./lib/active_support/ordered_hash.rb:150:in `each'
    ./lib/active_support/ordered_hash.rb:150:in `each'

In ruby 1.9, the above works fine for ordered hashes.