X dies after upgrade

[Gareth de Vaux <debian@lordcow.org>]

Hi all, I can't find any similar issues on this list - I upgraded my system
tracking debian testing yesterday but it's been awhile given by the Xorg
changelog at http://lordcow.org/Xorg.changelog.txt and now X doesn't start.

I installed xserver-xorg-legacy and added needs_root_rights=yes to
/etc/X11/Xwrapper.config just incase it was that. I tried creating an
xorg.conf and setting the driver to intel for older hardware as suggested
but this doesn't help. X seems to flash up for a split second but then
terminates. The unhelpful log is at http://lordcow.org/Xorg.0.log .

I'm getting nowhere trying different drivers and configs, does anyone
have an idea? Some specs:

from lspci -v:
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09) (prog-if 00 [VGA controller])
	Subsystem: Gigabyte Technology Co., Ltd 2nd Generation Core Processor Family Integrated Graphics Controller
	Flags: bus master, fast devsel, latency 0, IRQ 30
	Memory at fb800000 (64-bit, non-prefetchable) [size=4M]
	Memory at e0000000 (64-bit, prefetchable) [size=256M]
	I/O ports at ff00 [size=64]
	[virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
	Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
	Capabilities: [d0] Power Management version 2
	Capabilities: [a4] PCI Advanced Features
	Kernel driver in use: i915
	Kernel modules: i915

$ dpkg -l | grep Intel
ii  i965-va-driver:amd64                  1.7.1-1                           amd64        VAAPI driver for Intel G45 & HD Graphics family
ii  libcilkrts5:amd64                     6.1.1-10                          amd64        Intel Cilk Plus language extensions (runtime)
ii  libmpx0:amd64                         5.4.0-6                           amd64        Intel memory protection extensions (runtime)
ii  xserver-xorg-video-intel              2:2.99.917+git20160706-1          amd64        X.Org X server -- Intel i8xx, i9xx display driver

$ lsmod | grep i915
i915                 1245184  1
video                  40960  1 i915
drm_kms_helper        147456  1 i915
drm                   360448  3 i915,drm_kms_helper
i2c_algo_bit           16384  1 i915
button                 16384  1 i915

$ cat /etc/issue
Debian GNU/Linux stretch/sid \n \l

$ uname -a
Linux fire 4.6.0-1-amd64 #1 SMP Debian 4.6.4-1 (2016-07-18) x86_64 GNU/Linux