re-introduce pytest._fillfuncargs - it's actually used by oejskit,

added a test documenting this.

_pytest/python.py

@@ -34,7 +34,7 @@ def pytest_namespace():
         'collect': {
         'Module': Module, 'Class': Class, 'Instance': Instance,
         'Function': Function, 'Generator': Generator,
-        }
+        '_fillfuncargs': fillfuncargs}
     }
 
 def pytest_funcarg__pytestconfig(request):

testing/test_python.py

@@ -517,6 +517,10 @@ def test_callspec_repr():
     repr(cs)
 
 class TestFillFuncArgs:
+    def test_fillfuncargs_exposed(self):
+        # used by oejskit
+        assert pytest._fillfuncargs == funcargs.fillfuncargs
+
     def test_funcarg_lookupfails(self, testdir):
         testdir.makeconftest("""
             def pytest_funcarg__xyzsomething(request):