IPC pipes don't work well (Windows).

If I pass ipc=True, then accept() will fail with a "Resource temporarily
unavailable" error. This is probably a libuv bug. For now, make ipc=False the
default.
Windows compile fixes.

Windows does not have unistd.h. Not sure why I included it in the first place.
Probably a left-over from a previous version.
Do not call start_read() twice.

This will work on Posix, but not on Windows.
Use a proper pipe name on Windows.

On Windows, named pipes are not file system objects but live in their own
namespace.
Windows is working now.