Provide __module__ attributes for functions defined in C and Python.

__module__ is the string name of the module the function was defined
in, just like __module__ of classes.  In some cases, particularly for
C functions, the __module__ may be None.

Change PyCFunction_New() from a function to a macro, but keep an
unused copy of the function around so that we don't change the binary
API.

Change pickle's save_global() to use whichmodule() if __module__ is
None, but add the __module__ logic to whichmodule() since it might be
used outside of pickle.

Include/funcobject.h

@@ -17,6 +17,7 @@ typedef struct {
     PyObject *func_name;
     PyObject *func_dict;
     PyObject *func_weakreflist;
+    PyObject *func_module;
 } PyFunctionObject;
 
 PyAPI_DATA(PyTypeObject) PyFunction_Type;
@@ -26,6 +27,7 @@ PyAPI_DATA(PyTypeObject) PyFunction_Type;
 PyAPI_FUNC(PyObject *) PyFunction_New(PyObject *, PyObject *);
 PyAPI_FUNC(PyObject *) PyFunction_GetCode(PyObject *);
 PyAPI_FUNC(PyObject *) PyFunction_GetGlobals(PyObject *);
+PyAPI_FUNC(PyObject *) PyFunction_GetModule(PyObject *);
 PyAPI_FUNC(PyObject *) PyFunction_GetDefaults(PyObject *);
 PyAPI_FUNC(int) PyFunction_SetDefaults(PyObject *, PyObject *);
 PyAPI_FUNC(PyObject *) PyFunction_GetClosure(PyObject *);
@@ -37,6 +39,8 @@ PyAPI_FUNC(int) PyFunction_SetClosure(PyObject *, PyObject *);
         (((PyFunctionObject *)func) -> func_code)
 #define PyFunction_GET_GLOBALS(func) \
 	(((PyFunctionObject *)func) -> func_globals)
+#define PyFunction_GET_MODULE(func) \
+	(((PyFunctionObject *)func) -> func_module)
 #define PyFunction_GET_DEFAULTS(func) \
 	(((PyFunctionObject *)func) -> func_defaults)
 #define PyFunction_GET_CLOSURE(func) \