tools: various things just to build test

- Remove python prefix
- Add spice build on qemu-xen
- Add usbredir build on qemu-xen

NOTE:
This patch is only for do fast test build with make debball
and upstream qemu build with spice full features.

Signed-off-by: Fabio Fantoni <fabio.fantoni@m2r.biz>
tools: Improve make debball

- Remove version from installed package name for correct update
- Add conffiles to manage main config files on package update
- Add/remove/stop of main services (xencommons, xendomains)
- Added on description that this make a build for testing only.

Changes from v3:
- Removed xend config file to avoid error if xend is disabled.

Changes from v2:
- Improved description.
- Improved add/remove of main service and added the stop.

NOTE:
This patch was rejected from upstream. I posted it if someone
want do fast and working test builds with deb.

Signed-off-by: Fabio Fantoni <fabio.fantoni@m2r.biz>
libxl: Add qxl vga interface support for upstream qemu

Usage:
  vga="qxl"

Changes from v15:
- refresh

Changes from v14:
- refresh
- small code impromevents on libxl_dm.c

Changes from v13:
- refresh
- update qemu parameters (from -vga to -device)

NOTE:
Seems needed other changes/fixes on xen side before
have it full working.
After latest Jan Beulich patches doesn't show any other
visible xen errors (at least I can't see them).

Signed-off-by: Fabio Fantoni <fabio.fantoni@m2r.biz>
Signed-off-by: Zhou Peng <zpengxen@gmail.com>
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: George Dunlap <george.dunlap@eu.citrix.com>