qemu: change to .tar.xz format

And use the official download location.

Suggested-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit b79547014d0cdbf34aa4112a464a63f9e865b9ce)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/qemu/qemu.hash

@@ -1,2 +1,2 @@
 # Locally computed, tarball verified with GPG signature
-sha256 f62ab18a1fb9ff5b4c81ed44becc945b11581eff777618141bdb787da55d3638  qemu-2.8.1.1.tar.bz2
+sha256 7b50634d729dcabe4a96d74062832274fa2f4c883e82904f5e6955f801edab54  qemu-2.8.1.1.tar.xz

package/qemu/qemu.mk

@@ -5,8 +5,8 @@
 ################################################################################
 
 QEMU_VERSION = 2.8.1.1
-QEMU_SOURCE = qemu-$(QEMU_VERSION).tar.bz2
-QEMU_SITE = http://wiki.qemu.org/download
+QEMU_SOURCE = qemu-$(QEMU_VERSION).tar.xz
+QEMU_SITE = http://download.qemu.org
 QEMU_LICENSE = GPLv2, LGPLv2.1, MIT, BSD-3c, BSD-2c, Others/BSD-1c
 QEMU_LICENSE_FILES = COPYING COPYING.LIB
 # NOTE: there is no top-level license file for non-(L)GPL licenses;