Backport of 1.9-1.11:

Backport of 1.9-1.11:
- Flush screen buffer upon console.flush() and output.flush().
This fixes bug #511992.
- Changes by Donovan Preston (and a few minor ones by me) to make IDE run under
MachoPython. Mainly making sure we don't call routines that don't exist
and representing pathnames in a os.separator-neutral format.

These shouldn't interfere too much with Just's work on the next generation IDE,
I hope.
- Modified version of patch #496882: echo SimpleStdin readline()
input to stdout.