Patch to allow mixed strings and named association for joins

From the RoR docs at

http://api.rubyonrails.org/classes/ActiveRecord/Base.html

:joins - Either an SQL fragment for additional joins like "LEFT JOIN
comments ON comments.post_id = id" (rarely needed), named associations
in the same form used for the :include option, which will perform
anINNER JOIN on the associated table(s), or an array containing a
mixture of both strings and named associations.

When using the "array containing a mixture of both strings and named
associations", for example

:joins => ['LEFT JOIN foos ON foo_id = foos.id', :bar]

the following error is raised:

Association named 'LEFT JOIN foos ON foo_id = foos.id' was not found;
perhaps you misspelled it?

The following patch allows arrays containing a mix of strings and
symbols. Please include this in ActiveRecord 2.3.6.

Index: base.rb

Looks good. Patch is missing tests though. You should also open a
lighthouse ticket and upload the tested patch there using git
format-patch - http://guides.rubyonrails.org/contributing_to_rails.html#create-a-patch