Prevent warning: unused function '__pyx_pw_5numpy_7ndarray_1__getbuffer__'

Originally fixed in 6cc61605, but a regression was later introduced in
519a19a9.

--HG--
extra : transplant_source : e%B0%AA%A0O%D0%06%1F%90%17%9C%0B%B3KN%84%17%E5%19%81

Cython/Compiler/Nodes.py

@@ -2942,8 +2942,15 @@ class DefNodeWrapper(FuncDefNode):
                 "PyObject *%s, PyObject *%s"
                     % (Naming.args_cname, Naming.kwds_cname))
         arg_code = ", ".join(arg_code_list)
+
+        # Prevent warning: unused function '__pyx_pw_5numpy_7ndarray_1__getbuffer__'
+        mf = ""
+        if (entry.name in ("__getbuffer__", "__releasebuffer__")
+            and entry.scope.is_c_class_scope):
+            mf = "CYTHON_UNUSED "
+
         dc = self.return_type.declaration_code(entry.func_cname)
-        header = "static %s(%s)" % (dc, arg_code)
+        header = "static %s%s(%s)" % (mf, dc, arg_code)
         code.putln("%s; /*proto*/" % header)
 
         if proto_only: