amend __new__ test

nogil_test/cypclass_test___new__.pyx

 cdef cypclass SomeMemory:
   int a
-  SomeMemory __new__(self):
-    o = new SomeMemory()
+
+  @staticmethod
+  SomeMemory __new__(void* (*f)()):
+    o = <SomeMemory> f()
     o.a = -2
     return o
 
-  void* __new__(self, int a):
-    o = new SomeMemory()
+  @staticmethod
+  void* __new__(void* (*f)(), int a):
+    o = <SomeMemory> f()
     o.a = a
     return <void*> o
 
+  @staticmethod
+  SomeMemory __alloc__():
+      return new SomeMemory()
+
   void __init__(self):
     this.a += 1