add missing field name 'lang'

Fix NotSupportedError exception which appears when searching fields by
description:
NotSupportedError: input of anonymous composite types is not implemented
"LINE 1: ...ND ir_translation.res_id = 0 AND ir_translation = E'en_US' A..."

issue2210
review158001

trytond/model/modelsql.py

@@ -1659,7 +1659,7 @@ class ModelSQL(ModelStorage):
                                 'ON (ir_translation.name = ' \
                                         'ir_model.model||\',\'||%s.name ' \
                                     'AND ir_translation.res_id = 0 ' \
-                                    'AND ir_translation = %%s ' \
+                                    'AND ir_translation.lang = %%s ' \
                                     'AND ir_translation.type = \'%s\' ' \
                                     'AND ir_translation.fuzzy = %s)' % \
                                 (table._table, ttype,