upon uninstall (purge), modprobe conf files aren't removed

[fabtagon]

When uninstalling fglrx (e.g. after finding out your graphics card is too old for that) using purge, the config files generated by the package remain, specifically

alternatives/x86_64-linux-gnu_fglrxcore_modconf
modprobe.d/fglrx-core.conf

As they blacklist a number of alternative drivers, notably the open source radeon driver (alias radeon off), X11 experience is creepy afterwards (software rendering, no reliable display resolution detection etc.).

dpkg -S doesn't show an owning package for above files.

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: fglrx (not installed)
ProcVersionSignature: Ubuntu 4.2.0-25.30-generic 4.2.6
Uname: Linux 4.2.0-25-generic x86_64
.tmp.unity.support.test.1:

ApportVersion: 2.19.1-0ubuntu5
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: compiz
CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0'
CompositorUnredirectFSW: true
CurrentDesktop: Unity
Date: Sun Jan 24 17:20:16 2016
DistUpgraded: 2015-10-30 17:50:35,563 DEBUG icon theme changed, re-reading
DistroCodename: wily
DistroVariant: ubuntu
DkmsStatus: fglrx-core, 15.201, 4.2.0-25-generic, x86_64: installed
GraphicsCard:
 Advanced Micro Devices, Inc. [AMD/ATI] RV710 [Radeon HD 4350/4550] [1002:954f] (prog-if 00 [VGA controller])
   Subsystem: ASUSTeK Computer Inc. Device [1043:02a8]
InstallationDate: Installed on 2015-04-27 (271 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
JournalErrors:
 No journal files were found.
 -- No entries --
MachineType: Gigabyte Technology Co., Ltd. To be filled by O.E.M.
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=sv_SE.UTF-8
 SHELL=
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.2.0-25-generic root=UUID=e3d55663-31b8-43f3-bb45-41c003d38364 ro quiet splash vt.handoff=7
Renderer: Software
SourcePackage: fglrx-installer
UdevLog: Error: [Errno 2] Filen eller katalogen finns inte: '/var/log/udev'
UpgradeStatus: Upgraded to wily on 2015-10-30 (85 days ago)
dmi.bios.date: 08/06/2013
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: F1
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: 970A-UD3P
dmi.board.vendor: Gigabyte Technology Co., Ltd.
dmi.board.version: x.x
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: Gigabyte Technology Co., Ltd.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrF1:bd08/06/2013:svnGigabyteTechnologyCo.,Ltd.:pnTobefilledbyO.E.M.:pvrTobefilledbyO.E.M.:rvnGigabyteTechnologyCo.,Ltd.:rn970A-UD3P:rvrx.x:cvnGigabyteTechnologyCo.,Ltd.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.name: To be filled by O.E.M.
dmi.product.version: To be filled by O.E.M.
dmi.sys.vendor: Gigabyte Technology Co., Ltd.
version.compiz: compiz 1:0.9.12.2+15.10.20151015-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.64-1
version.libgl1-mesa-dri: libgl1-mesa-dri 11.0.2-1ubuntu4
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 11.0.2-1ubuntu4
version.xserver-xorg-core: xserver-xorg-core 2:1.17.2-1ubuntu9.1
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.9.2-1ubuntu1
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.5.0+git20150819-0ubuntu1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20150808-0ubuntu4
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.11-1ubuntu3
xserver.bootTime: Sun Jan 24 17:04:23 2016
xserver.configfile: default
xserver.devices:
 input Power Button KEYBOARD, id 6
 input Power Button KEYBOARD, id 7
 input Silitek SILITEK USB KEYBOARD KEYBOARD, id 8
 input Silitek SILITEK USB KEYBOARD KEYBOARD, id 9
 input Logitech USB Optical Mouse MOUSE, id 10
xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:

xserver.version: 2:1.17.2-1ubuntu9.1