Add testcase for https://github.com/cython/cython/pull/1728

tests/run/cyfunction_METH_O_GH1728.pyx

+# cython: binding=True
+# mode: run
+# tag: cyfunction
+
+cdef class TestMethodOneArg:
+    def meth(self, arg):
+        pass
+
+def call_meth(x):
+    """
+    >>> call_meth(TestMethodOneArg())
+    Traceback (most recent call last):
+    ...
+    TypeError: meth() takes exactly one argument (0 given)
+    """
+    return x.meth()