gnu: qemu: Add fixes for CVE-2015-{4037,4103,4104,4105,4106}.

* gnu/packages/patches/qemu-CVE-2015-4037.patch,
  gnu/packages/patches/qemu-CVE-2015-4103.patch,
  gnu/packages/patches/qemu-CVE-2015-4104.patch,
  gnu/packages/patches/qemu-CVE-2015-4105.patch,
  gnu/packages/patches/qemu-CVE-2015-4106-pt1.patch,
  gnu/packages/patches/qemu-CVE-2015-4106-pt2.patch,
  gnu/packages/patches/qemu-CVE-2015-4106-pt3.patch,
  gnu/packages/patches/qemu-CVE-2015-4106-pt4.patch,
  gnu/packages/patches/qemu-CVE-2015-4106-pt5.patch,
  gnu/packages/patches/qemu-CVE-2015-4106-pt6.patch,
  gnu/packages/patches/qemu-CVE-2015-4106-pt7.patch,
  gnu/packages/patches/qemu-CVE-2015-4106-pt8.patch: New files.
* gnu-system.am (dist_patch_DATA): Add them.
* gnu/packages/qemu.scm (qemu-headless)[source]: Add patches.