Removing zope.app.appsetup as a dependency

zope.app.appsetup drags in most of the rest of Zope 3,
which is not needed to only extract i18n strings from ZCML,
so I copied in the relevant code (and simplified it).

setup.py

@@ -74,7 +74,6 @@ def read(*rnames):
               ],
           extract=[
               'zope.tal',
-              'zope.app.appsetup',
               ],
           ),
       include_package_data = True,

src/zope/app/locales/extract.py

@@ -483,9 +483,14 @@ def py_strings(dir, domain="zope", exclude=(), verify_domain=False):
 def zcml_strings(dir, domain="zope", site_zcml=None):
     """Retrieve all ZCML messages from `dir` that are in the `domain`.
     """
-    from zope.app.appsetup import config
-    dirname = os.path.dirname
-    context = config(site_zcml, features=("devmode",), execute=False)
+    from zope.configuration import xmlconfig, config
+
+    # Load server-independent site config
+    context = config.ConfigurationMachine()
+    xmlconfig.registerCommonDirectives(context)
+    context.provideFeature("devmode")
+    context = xmlconfig.file(site_zcml, context=context, execute=False)
+
     return context.i18n_strings.get(domain, {})
 
 def tal_strings(dir,