Fix missing '__file__' when running scripts.

--HG--
branch : setuptools
extra : convert_revision : svn%3A6015fed2-1504-0410-9fe1-9d1591cc4771/sandbox/trunk/setuptools%4041058

pkg_resources.py

@@ -587,7 +587,7 @@ class NullProvider:
         script_text = self.get_metadata(script).replace('\r\n','\n')
         script_text = script_text.replace('\r','\n')
         script_filename = self._fn(self.egg_info,script)
-
+        namespace['__file__'] = script_filename
         if os.path.exists(script_filename):
             execfile(script_filename, namespace, namespace)
         else: