Bring back postgresql_version as an alias.

Author: simi

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -425,6 +425,7 @@ def column_name_for_operation(operation, node) # :nodoc:
       def get_database_version
         @connection.server_version
       end
+      alias :postgresql_version :database_version
 
       def default_index_type?(index) # :nodoc:
         index.using == :btree || super