use a more generic variant, so that we can run the tests unmodified also on PyPy

Author: antocuni

test/support.py

@@ -170,7 +170,7 @@ def make_module(self, source_template, name='mytest', extra_templates=()):
 
     def should_check_refcount(self):
         # defaults to True on CPython, but is set to False by e.g. PyPy
-        return True
+        return sys.implementation.name == 'cpython'
 
 
 # the few functions below are copied and adapted from cffi/ffiplatform.py