Fix setting of MySQL native database types in Ruby 1.8
Fix setting of MySQL native database types in Ruby 1.8

 * There are differences in constant lookup between 1.8 and 1.9 when inside a class_eval block.
juniorz/spatial_adapter,darbyfrey/spatial_adapter,bellycard/spatial_adapter,smedrick/spatial_adapter,julianray/spatial_adapter,jsack777/spatial_adapter,pdeffendol/spatial_adapter,hashbangnz/spatial_adapter