make an old test from 'broken' directory usable

tests/broken/r_extcmethod.pyx

-cdef class SpamDish:
-    cdef int spam
-
-    cdef void describe(self):
-        print "This dish contains", self.spam, "tons of spam."
-
-
-cdef class FancySpamDish(SpamDish):
-    cdef int lettuce
-
-    cdef void describe(self):
-        print "This dish contains", self.spam, "tons of spam",
-        print "and", self.lettuce, "milligrams of lettuce."
-
-
-cdef void describe_dish(SpamDish d):
-    d.describe()
-
-def test():
-    cdef SpamDish s
-    cdef FancySpamDish ss
-    s = SpamDish()
-    s.spam = 42
-    ss = FancySpamDish()
-    ss.spam = 88
-    ss.lettuce = 5
-    describe_dish(s)
-    describe_dish(ss)