avoid using sys.getrefcount() where possible (PyPy doesn't have it)

tests/run/exceptionrefcount.pyx

 __doc__ = u"""
 >>> class SampleException(Exception): pass
->>> import sys
 
 >>> def assert_refcount(rc1, rc2, func):
 ...     # test ref-counts, but allow a bit of freedom
@@ -8,17 +7,17 @@ __doc__ = u"""
 ...         func.__name__, rc1, rc2)
 
 >>> def run_test(repeat, test_func):
-...     initial_refcount = sys.getrefcount(SampleException)
+...     initial_refcount = get_refcount(SampleException)
 ...     for i in range(repeat):
 ...         try: raise SampleException
 ...         except:
-...             refcount1 = sys.getrefcount(SampleException)
+...             refcount1 = get_refcount(SampleException)
 ...             test_func()
-...             refcount2 = sys.getrefcount(SampleException)
+...             refcount2 = get_refcount(SampleException)
 ...
 ...             assert_refcount(refcount1, refcount2, test_func)
 ...             assert_refcount(initial_refcount, refcount2, test_func)
-...         refcount3 = sys.getrefcount(SampleException)
+...         refcount3 = get_refcount(SampleException)
 ...         assert_refcount(refcount1, refcount3, test_func)
 ...         assert_refcount(initial_refcount, refcount3, test_func)
 
@@ -28,6 +27,11 @@ __doc__ = u"""
 >>> run_test(50, test_finally)
 """
 
+from cpython.ref cimport PyObject
+
+def get_refcount(obj):
+    return (<PyObject*>obj).ob_refcnt
+
 def test_no_exception():
     try:
         a = 1+1

tests/run/refcount_in_meth.pyx

@@ -12,7 +12,10 @@ True
 True
 """
 
-import sys
+from cpython.ref cimport PyObject
+
+def get_refcount(obj):
+    return (<PyObject*>obj).ob_refcnt
 
 cdef class RefCountInMeth(object):
     cdef double value
@@ -32,27 +35,27 @@ cdef class RefCountInMeth(object):
     cdef int c_meth(self):
         cdef int v
 
-        v = sys.getrefcount(self)
+        v = get_refcount(self)
         return v
 
     cdef int c_meth_if(self):
         cdef int v
         if 5>6:
             v = 7
-        v = sys.getrefcount(self)
+        v = get_refcount(self)
         return v
 
     def chk_meth(self):
         cdef int a,b
 
-        a = sys.getrefcount(self)
+        a = get_refcount(self)
         b = self.c_meth()
         return a==b
 
     def chk_meth_if(self):
         cdef int a,b
 
-        a = sys.getrefcount(self)
+        a = get_refcount(self)
         b = self.c_meth_if()
         return a==b