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 none to vga parameter

Usage:
  vga="none"

Make possible to not have an emulated vga on hvm domUs.

Signed-off-by: Fabio Fantoni <fabio.fantoni@m2r.biz>

---

Changes in v4:
- set video_memkb to 0 only if the default was not changed

Changes in v3:
- set video_memkb to 0 if vga is none.
- remove a check on one condition no more needed.

Changes in v2:
- libxl_dm.c:
 if vga is none, on qemu traditional:
  - add -vga none parameter.
  - do not add -videoram parameter.