windows: Set fAbortOnError=FALSE.

windows: Set fAbortOnError=FALSE.

Since we're not handling and clearing receive errors (framing, parity and
overrun), we should turn them off to avoid crashing out with
ERROR_OPERATION_ABORTED in various calls if they occur. Invalid data
will then simply not end up in the buffer. This is consistent with our
current behaviour on posix/termios systems.

It might be nice to be able to inform calling code about receive errors, but I
can't see a good way to do this in a cross-platform way at the moment.

This fixes (parts of) bug #341.