mysql_adapter.rb redefines all_hashes multiple times under ruby 1.9

The instance_methods test in mysql_adapter.rb is not correct as ruby 1.9 returns symbols in instance_methods and not strings.

This simple patch adds an or condition to accept either:

return if target.instance_methods.include?('all_hashes') ||

        target.instance_methods.include?(:all_hashes)

Adding this patch prevents all_hashes being redefined each time a connection is made.