sdlaudio: replace legacy functions with modern ones

With the modern audio functions it's possible to add new
features like audio recording.

As a side effect this patch fixes a bug where SDL2 can't be used
on Windows. This bug was reported on the qemu-devel mailing list at

https://lists.nongnu.org/archive/html/qemu-devel/2020-01/msg04043.html



Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-id: 9315afe5-5958-c0b4-ea1e-14769511a9d5@t-online.de
Message-Id: <20210110100239.27588-7-vr_qemu@t-online.de>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>