[ADD] base: warning for external id in the wrong module

Creating a external id in a different module than the one where the record is
declared is a bad practice.
Setting a correct module is both important for a correct uninstallation of the
module (which uses the module to decide which records to remove) and for the
translations (records tagged with 'base' module needs to be declared in the
base.pot file).

openerp/addons/base/ir/ir_model.py

@@ -1001,6 +1001,7 @@ class IrModelData(models.Model):
     def _update(self, model, module, values, xml_id=False, store=True, noupdate=False, mode='init', res_id=False):
         # records created during module install should not display the messages of OpenChatter
         self = self.with_context(install_mode=True)
+        current_module = module
 
         if xml_id and ('.' in xml_id):
             assert len(xml_id.split('.')) == 2, _("'%s' contains too many dots. XML ids should not contain dots ! These are used to refer to other modules data, as in module.reference_id") % xml_id
@@ -1088,6 +1089,10 @@ class IrModelData(models.Model):
                     'res_id': record.id,
                     'noupdate': noupdate
                 })
+                if current_module and module != current_module:
+                    _logger.warning("Creating the ir.model.data %s in module %s instead of %s.",
+                                    xml_id, module, current_module)
+
 
         if xml_id and record:
             self.loads[(module, xml_id)] = (model, record.id)