qemu: updgrade to 2.5.1

qemu: updgrade to 2.5.1

This upgrade includes several worthwhile fixes, security and otherwise, including
a complete fix for CVE-2016-2857.

* drop CVE-2016-2857.patch as it's included in this release, along with several
  related patches which complete the fixes for CVE-2016-2857:
  http://git.qemu.org/?p=qemu.git;a=commitdiff;h=9bddb45dbc010cd8ee4d48bd501fa5d18dcec00c
  http://git.qemu.org/?p=qemu.git;a=commitdiff;h=e3a2cdfcb5e282139217924044ec5af00c7f8eed
  http://git.qemu.org/?p=qemu.git;a=commitdiff;h=fe90bdc25bcf9954ee286cd51de94776a17d04f6
  http://git.qemu.org/?p=qemu.git;a=commitdiff;h=d0ee85b4e4c6cc2c8fac311d6df2ed412ed0df5f
  http://git.qemu.org/?p=qemu.git;a=commitdiff;h=80b6e5723fac428ea6c08c821078286f43975df8
  http://git.qemu.org/?p=qemu.git;a=commitdiff;h=a375e0b03ee3438924b24a45e61ee189ec9361db
* drop CVE-2016-2197.patch as an equivalent fix is included in this release
  http://git.qemu.org/?p=qemu.git;a=commitdiff;h=aaf4fb6afb4653c86059255811886a5c4ea271f3
* drop CVE-2016-1568.patch as it's included in this release
  http://git.qemu.org/?p=qemu.git;a=commitdiff;h=4f046a6ba1d558eb043dc13a80d40cf7cb62ef95

Signed-off-by: Joshua Lock <joshua.g.lock@intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>