Add cyfunction tests

tests/run/cyfunction.pyx

+# cython: binding=True
+# mode: run
+# tag: cyfunction
+
+def test_dict():
+    """
+    >>> test_dict.foo = 123
+    >>> test_dict.__dict__
+    {'foo': 123}
+    """
+
+def test_name():
+    """
+    >>> test_name.__name__
+    'test_name'
+    """
+
+def test_reduce():
+    """
+    >>> import pickle
+    >>> pickle.loads(pickle.dumps(test_reduce))()
+    'Hello, world!'
+    """
+    return 'Hello, world!'
+
+def test_method(self):
+    return self
+
+class BindingTest:
+    """
+    >>> BindingTest.test_method = test_method
+    >>> BindingTest.test_method() #doctest:+ELLIPSIS
+    Traceback (most recent call last):
+    TypeError: ...
+    >>> BindingTest().test_method()
+    <BindingTest instance>
+    """
+    def __repr__(self):
+        return '<BindingTest instance>'