main_loop_wait: block indefinitely

- remove qemu_calculate_timeout;

- explicitly size timeout to uint32_t;

- introduce slirp_update_timeout;

- pass NULL as timeout argument to select in case timeout is the maximum
value;

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Paul Brook <paul@codesourcery.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/async.c b/async.c
index 332d511..ecdaf15 100644
--- a/async.c
+++ b/async.c
@@ -120,7 +120,7 @@
     bh->deleted = 1;
 }
 
-void qemu_bh_update_timeout(int *timeout)
+void qemu_bh_update_timeout(uint32_t *timeout)
 {
     QEMUBH *bh;