qemu-system-x86-xen landed in Debian but under a different name.
Therefore we:
- no more need the alternate depends as they are no more mutually
  exclusive
- need a transitional for the name change
- need breaks/replace for the name change

Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>

Disable xen support for regular qemu-system-x86 binaries, since it is
now enabled in a separate qemu-system-xen package.  Make qemu-system-i386
to be a wrapper script that either calls regular qemu-system-i386 binary
or xen-specific qemu-system-i386-xen if xen-specific arguments are being
used, and the xen-specific binary exists. And print a warning to update
the configuration.

Revert "d/rules: do not try to enable tcg-interpreter on unsupported targets, it does not help anymore"

This reverts commit 608475dd.

Apparently this helps but needs some more work with current qemu

a patch from upstream

coroutine-use-QEMU_DEFINE_STATIC_CO_TLS.patch
coroutine-rename-qemu_coroutine_inc-dec_pool_size.patch
coroutine-revert-to-constant-batch-size.patch

virtio-scsi-fix-ctrl-and-event-handler-functions-in-dataplane.patch
virtio-scsi-don-t-waste-CPU-polling-the-event-virtqueue.patch

the previous binfmt changes did not actually work due to the wrong
names of binfmt.d/ files. It is foo.conf not foo, so all qemu format
files were ignored.

This reverts commit 1d184984.

Since salsa-ci does not work right, we do not have to keep d/control in git

use dpkg --print-architecture to determine the default architecture,
instead of using dpkg-architecture (which requires gcc).  We need the
architecture of our base backages anyway.

Use a table (case..esac) of various possible ways to specify architecture
into qemu architecture. All tools that print current/default architecture
need one or another correction anyway.

Test qemu-user-static too, not only qemu-user.

Do a more useful test there, to include /bin/sh, /bin/ls -l, and globbing.

d/tests/qemu-user: depend on gcc for dpkg-architecture, and print debugging to switch to uname-m in future

mjt: add Restriction: superficial, use $AUTOPKGTEST_TMP, avoid ? shell metachars