Variation of patch # 1624059 to speed up checking if an object is a subclass

of some of the common builtin types.

Use a bit in tp_flags for each common builtin type.  Check the bit
to determine if any instance is a subclass of these common types.
The check avoids a function call and O(n) search of the base classes.
The check is done in the various Py*_Check macros rather than calling
PyType_IsSubtype().

All the bits are set in tp_flags when the type is declared
in the Objects/*object.c files because PyType_Ready() is not called
for all the types.  Should PyType_Ready() be called for all types?
If so and the change is made, the changes to the Objects/*object.c files
can be reverted (remove setting the tp_flags).  Objects/typeobject.c
would also have to be modified to add conditions
for Py*_CheckExact() in addition to each the PyType_IsSubtype check.

Objects/unicodeobject.c

@@ -7967,7 +7967,7 @@ PyTypeObject PyUnicode_Type = {
     0,			 		/* tp_setattro */
     &unicode_as_buffer,			/* tp_as_buffer */
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_CHECKTYPES |
-	    Py_TPFLAGS_BASETYPE,	/* tp_flags */
+	    Py_TPFLAGS_BASETYPE | Py_TPFLAGS_UNICODE_SUBCLASS,	/* tp_flags */
     unicode_doc,			/* tp_doc */
     0,					/* tp_traverse */
     0,					/* tp_clear */