Refactor future feature handling

Replace individual slots in PyFutureFeatures with a single bitmask
with one field per feature.  The flags for this bitmask are the same
as the flags used in the co_flags slot of a code object.

    XXX This means we waste several bits, because they are used
    for co_flags but have no meaning for future statements.  Don't
    think this is an issue.

Remove the NESTED_SCOPES_DEFAULT define and others.  Not sure what
they were for anyway.

Remove all the PyCF_xxx flags, but define PyCF_MASK in terms of the
CO_xxx flags that are relevant for this release.

Change definition of PyCompilerFlags so that cf_flags matches
co_flags.

Include/compile.h

@@ -41,7 +41,6 @@ typedef struct {
    effect, this passes on the "from __future__ import generators" state
    in effect when the code block was compiled. */
 #define CO_GENERATOR_ALLOWED    0x1000
-/* XXX Ditto for future division */
 #define CO_FUTURE_DIVISION    	0x2000
 
 extern DL_IMPORT(PyTypeObject) PyCode_Type;
@@ -64,22 +63,15 @@ DL_IMPORT(int) PyCode_Addr2Line(PyCodeObject *, int);
 typedef struct {
     int ff_found_docstring;
     int ff_last_lineno;
-    int ff_nested_scopes;
-    int ff_generators;
-    int ff_division;
+    int ff_features;
 } PyFutureFeatures;
 
 DL_IMPORT(PyFutureFeatures *) PyNode_Future(struct _node *, char *);
 DL_IMPORT(PyCodeObject *) PyNode_CompileFlags(struct _node *, char *,
 					      PyCompilerFlags *);
 
-#define NESTED_SCOPES_DEFAULT 1
 #define FUTURE_NESTED_SCOPES "nested_scopes"
-
-#define GENERATORS_DEFAULT 0
 #define FUTURE_GENERATORS "generators"
-
-#define DIVISION_DEFAULT 0
 #define FUTURE_DIVISION "division"
 
 /* for internal use only */

Include/pythonrun.h

@@ -7,14 +7,9 @@
 extern "C" {
 #endif
 
-/* These flags are named after the __future__ statements that introduced
-   them.  May not remain true for later additions, so fiddle this comment
-   accordingly then. */
-#define PyCF_NESTED_SCOPES	(0x00000001UL)
-#define PyCF_GENERATORS		(0x00000002UL)
-#define PyCF_DIVISION		(0x00000004UL)
+#define PyCF_MASK (CO_GENERATOR_ALLOWED | CO_FUTURE_DIVISION)
 typedef struct {
-	unsigned long cf_flags;  /* bitmask of PyCF_xxx flags */
+	int cf_flags;  /* bitmask of CO_xxx flags relevant to future */
 } PyCompilerFlags;
 
 DL_IMPORT(void) Py_SetProgramName(char *);