aio: convert aio_poll() to g_poll(3)

AioHandler already has a GPollFD so we can directly use its
events/revents.

Add the int pollfds_idx field to AioContext so we can map g_poll(3)
results back to AioHandlers.

Reuse aio_dispatch() to invoke handlers after g_poll(3).

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-id: 1361356113-11049-10-git-send-email-stefanha@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/async.c b/async.c
index 72d268a..f2d47ba 100644
--- a/async.c
+++ b/async.c
@@ -174,6 +174,7 @@
 
     aio_set_event_notifier(ctx, &ctx->notifier, NULL, NULL);
     event_notifier_cleanup(&ctx->notifier);
+    g_array_free(ctx->pollfds, TRUE);
 }
 
 static GSourceFuncs aio_source_funcs = {
@@ -198,6 +199,7 @@
 {
     AioContext *ctx;
     ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
+    ctx->pollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
     event_notifier_init(&ctx->notifier, false);
     aio_set_event_notifier(ctx, &ctx->notifier, 
                            (EventNotifierHandler *)