msvcrt: Fix EOF behavior on read from pipe

[Dan Kegel]

Damjan wrote
> The problem is more general: consoles *also* break on short reads
> (Java 1.4.1's gdb takes 1 command then quits because it thinks it's
> the end of file)

Try my patch, it should help that case.

> I'm sure short read != end of file for ordinary
> files either, especially in *nix where read() can easily be
> interrupted by a signal.

If you can come up with an example of a real
app or even a test case that is currently broken,
I'll gladly try to fix it.
- Dan