bpo-38002: Use False/True for IDLE pyshell bools (GH-19203)

Change 0/1 assignments to 'executing', 'canceled', 'reading', 'endoffile'.
These are not used outside of pyshell. Other bools already use False/True.
Add comment about int needed for Windows call.
Remove self.more, unused in idlelib and code.InteractiveInterpreter.
The latter uses 'more' as a local.