Update spice to version 0.12.8

Update spice to version 0.12.8

This is an security update.
Recent were 2 serious security vulnerabilities published.
This patch update spice to a version which is not vulnerable.

Changelog:

Changes in 0.12.8:

==================
* Fixes for CVE-2016-0749 and CVE-2016-2150

Changes in 0.12.7:
==================
* spice-server will now send TCP keepalive probes on the TCP connections
  it
  uses. This can prevent unwanted idle disconnections if proxies are
  used
  between the client and the host.
* Fix important memory usage when the webdav channel is used
* Do not disconnect when the client requests an unsupported compression
  type
* Fix a few race conditions
* Fix display glitch when using XSpice
* Improve help string for 'replay -s'
* Fix crashes in corner cases (buggy spice-html5 + win10, vnc + SPICE
  port
  configured, USB webcam redirection over a slow link)
* Fix various compilation warning when building on 32 bit machines
* Some fixes for big-endian machines, more work is likely to be needed
* Do not build static libraries by default, this can be reenabled with
  --enable-static
* Fix small leak in MJPEG code

Signed-off-by: Jonatan Schlag <jonatan.schlag@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>