simple test for extension class body

tests/run/extclassbody.pyx

+__doc__ = u"""
+>>> s = Spam()
+>>> s.a
+1
+>>> s.c
+3
+>>> s.test(5)
+8
+>>> s.b
+3
+"""
+
+cdef class Spam:
+    a = 1
+    def test(self, a):
+        return a + self.c
+    b = a + 2
+    c = 3