Improve comments.

Modules/_decimal/_decimal.c

@@ -1510,7 +1510,7 @@ current_context(void)
 #define CURRENT_CONTEXT_ADDR(ctx) \
     ctx = CTX(current_context())
 
-/* Return current context, increment reference */
+/* Return a new reference to the current context */
 static PyObject *
 PyDec_GetCurrentContext(void)
 {
@@ -1614,7 +1614,7 @@ current_context(void)
     ctx = CTX(_c_t_x_o_b_j);                    \
 }
 
-/* Return current context, increment reference */
+/* Return a new reference to the current context */
 static PyObject *
 PyDec_GetCurrentContext(void)
 {
@@ -1759,7 +1759,7 @@ static PyTypeObject PyDecContextManager_Type =
     0,                                      /* tp_print */
     (getattrfunc) 0,                        /* tp_getattr */
     (setattrfunc) 0,                        /* tp_setattr */
-    0,                                      /* tp_compare */
+    0,                                      /* tp_reserved */
     (reprfunc) 0,                           /* tp_repr */
     0,                                      /* tp_as_number */
     0,                                      /* tp_as_sequence */