Repair description of TEST_VALUE (the TEST_KEY text it referenced

vanished).

src/BTrees/Maintainer.txt

@@ -41,17 +41,16 @@ Tests whether the PyObject* K can be converted to the (C) key type
 non-zero for true).  When it returns false, its caller should probably
 set a TypeError exception.
 
-TEST_KEY_SET_OR(V, K, T) 
+TEST_KEY_SET_OR(V, K, T)
 Like Python's cmp().  Compares K(ey) to T(arget), where K & T are C
-data values of type KEY_TYPE).
+values of type KEY_TYPE.  V is assigned an int value depending on
+the outcome:
    < 0 if K < T
   == 0 if K == T
    > 0 if K > T
-The value is assigned to V. This macro acts like an 'if',
-where the following statement is executed only if a Python exception
-has been raised because the values could not be compared.
-
-
+This macro acts like an 'if', where the following statement is
+executed only if a Python exception has been raised because the
+values could not be compared.
 
 DECREF_KEY(K)
 K is a value of KEY_TYPE.  If KEY_TYPE is a flavor of PyObject*, write
@@ -85,8 +84,14 @@ Macros for Values
 VALUE_TYPE
 The C type declaration for values (e.g., int or PyObject*).
 
-TEST_VALUE(K, T)
-Like TEST_KEY, except applied to values of VALUE_TYPE.
+TEST_VALUE(X, Y)
+Like Python's cmp().  Compares X to Y, where X & Y are C values of
+type VALUE_TYPE.  The macro returns an int, with value
+   < 0 if X < Y
+  == 0 if X == Y
+   > 0 if X > Y
+XXX There is no provision for determining whether the comparison
+attempt failed (set a Python exception).
 
 DECREF_VALUE(K)
 Like DECREF_KEY, except applied to values of VALUE_TYPE.