Only setup_default_renderer if AppConfig.use_legacy_renderer is True (default).
Only setup_default_renderer if AppConfig.use_legacy_renderer is True (default).

This also renames AppConfig.use_legacy_render to use_legacy_renderer,
which is consistent with the setup_default_renderer docstring, as well
as the tg.controllers module.

--HG--
extra : convert_revision : svn%3A77541ad4-5f01-0410-9ede-a1b63cd9a898/trunk%405363

lucius-feng/tg2,lucius-feng/tg2