qemu-io: Add AIO debugging commands

This makes the blkdebug suspend/resume functionality available in
qemu-io. Use it like this:

  $ ./qemu-io blkdebug::/tmp/test.qcow2
  qemu-io> break write_aio req_a
  qemu-io> aio_write 0 4k
  qemu-io> blkdebug: Suspended request 'req_a'
  qemu-io> resume req_a
  blkdebug: Resuming request 'req_a'
  qemu-io> wrote 4096/4096 bytes at offset 0
  4 KiB, 1 ops; 0:00:30.71 (133.359788 bytes/sec and 0.0326 ops/sec)

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block.c b/block.c
index b3faf3a..0668c4b 100644
--- a/block.c
+++ b/block.c
@@ -3045,7 +3045,46 @@
     }
 
     drv->bdrv_debug_event(bs, event);
+}
 
+int bdrv_debug_breakpoint(BlockDriverState *bs, const char *event,
+                          const char *tag)
+{
+    while (bs && bs->drv && !bs->drv->bdrv_debug_breakpoint) {
+        bs = bs->file;
+    }
+
+    if (bs && bs->drv && bs->drv->bdrv_debug_breakpoint) {
+        return bs->drv->bdrv_debug_breakpoint(bs, event, tag);
+    }
+
+    return -ENOTSUP;
+}
+
+int bdrv_debug_resume(BlockDriverState *bs, const char *tag)
+{
+    while (bs && bs->drv && !bs->drv->bdrv_debug_resume) {
+        bs = bs->file;
+    }
+
+    if (bs && bs->drv && bs->drv->bdrv_debug_resume) {
+        return bs->drv->bdrv_debug_resume(bs, tag);
+    }
+
+    return -ENOTSUP;
+}
+
+bool bdrv_debug_is_suspended(BlockDriverState *bs, const char *tag)
+{
+    while (bs && bs->drv && !bs->drv->bdrv_debug_is_suspended) {
+        bs = bs->file;
+    }
+
+    if (bs && bs->drv && bs->drv->bdrv_debug_is_suspended) {
+        return bs->drv->bdrv_debug_is_suspended(bs, tag);
+    }
+
+    return false;
 }
 
 /**************************************************************/