Add Knuth's "man or boy" test.

tests/run/knuth_man_or_boy_test.pyx

+#
+# Cython version of Knuth's "man or boy" test -- "It separates the man
+# Algol 60 compilers from the boy Algol 60 compilers." Here's the
+# original (from wikipedia):
+#
+# begin
+#   real procedure A (k, x1, x2, x3, x4, x5);
+#   value k; integer k;
+#   begin
+#     real procedure B;
+#     begin k:= k - 1;
+#           B:= A := A (k, B, x1, x2, x3, x4);
+#     end;
+#     if k <= 0 then A:= x4 + x5 else B;
+#   end;
+#   outreal (A (10, 1, -1, -1, 1, 0));
+# end;
+#
+# and a table of values:
+#
+#   k           A
+#   0           1
+#   1           0
+#   2   	-2
+#   3   	0
+#   4   	1
+#   5   	0
+#   6   	1
+#   7   	-1
+#   8   	-10
+#   9   	-30
+#   10   	-67
+#
+# Past 10 or so, we blow the C stack -- can't just set a higher recursion limit
+# to get around that one.
+#
+
+def compute(val):
+    if isinstance(val, int):
+        return val
+    else:
+        return val()
+
+def a(in_k, x1, x2, x3, x4, x5):
+    """
+    >>> import sys
+    >>> sys.setrecursionlimit(1350)
+    >>> a(10, 1, -1, -1, 1, 0)
+    -67
+    """
+    k = [in_k]
+    def b():
+        k[0] -= 1
+        return a(k[0], b, x1, x2, x3, x4)
+    return compute(x4) + compute(x5) if k[0] <= 0 else b()
+