win32: port gtester to work on windows
@malureau
Submitted by Marc-André Lureau Link to original bug (#679656)
Description
The changes are mostly trivial. Only G_SPAWN_LEAVE_DESCRIPTORS_OPEN can't easily be fixed, the spawn-helper closes all fd > 3 if not set. There is no callback like on Linux to unset the CLOEXEC, or prevent from closing the fd. Perhaps we need an extended spawn_async_with_pipes() that would take a list of fd to leave open?