update to QEMU 5.1

No major semantic changes, mostly just deprecations and changed function
signatures. Drop the extra/ patches, as they have been applied upstream.

The added extra/ patch was accepted upstream[0] but has not been picked
up for 5.1. It is required for non-4M aligned backups to work with PBS.

[0] https://lists.gnu.org/archive/html/qemu-devel/2020-08/msg01671.html

Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>

debian/patches/pve/0023-PVE-monitor-disable-oob-capability.patch

@@ -18,10 +18,10 @@ Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
  1 file changed, 1 insertion(+), 2 deletions(-)
 
 diff --git a/monitor/qmp.c b/monitor/qmp.c
-index f89e7daf27..ed5e39fcf7 100644
+index d433ceae5b..a16cf3532d 100644
 --- a/monitor/qmp.c
 +++ b/monitor/qmp.c
-@@ -406,8 +406,7 @@ void monitor_init_qmp(Chardev *chr, bool pretty, Error **errp)
+@@ -409,8 +409,7 @@ void monitor_init_qmp(Chardev *chr, bool pretty, Error **errp)
      qemu_chr_fe_set_echo(&mon->common.chr, true);
  
      /* Note: we run QMP monitor in I/O thread when @chr supports that */