Bug 509446 - portable blocking gio cancellation
* gcancellable.c (g_cancellable_make_pollfd): New method to make a
GPollFD for a cancellable (which is slightly more complicated on
Windows than Unix).
* gunixinputstream.c (g_unix_input_stream_read):
* gunixoutputstream.c (g_unix_output_stream_write): Use
g_cancellable_make_pollfd() and g_poll() rather than using poll()
directly.
* tests/unix-streams.c: test of GUnixInputStream,
GUnixOutputStream, and GCancellable.
svn path=/trunk/; revision=7553
