disable composite in fglrx

Confirmed, dexconf needs to grow support for an Extensions section.

Maybe it would be even better to change xorg-server's 019_ubuntu_enable_composite.diff to not enable it on known-bad drivers like fglrx.

<tepsipakki> enabling Composite has been discussed in debian-x-list recently
<tepsipakki> and they prefer doing it via the config
<tepsipakki> we have patched xorg-server like fedora

Will fix in xorg.

 xorg (1:7.2-0ubuntu7) feisty; urgency=low
 .
   * debian/local/dexconf: Disable composite when using the fglrx driver. It
     does not support composition, and enabling it by default (as recently done
     in xorg-server) breaks DRI for fglrx. (LP: #90688)

I didn't really understand what this fix does. I thought that with this fix changing the driver from "ati" to "fglrx" was enough to disable composite. in my case I remove from xorg.conf the lines to disable composite, but the fix does nothing: composite is still enabled

(II) fglrx(0): Composite extension enabled, disabling direct rendering

xorg (1:7.2-3ubuntu1) gutsy; urgency=low

  * Merge from Debian unstable. Remaining changes:
    - debian/control, debian/scripts/vars.sparc, debian/rules:
      + Makes xorg Architecture: any and use an extra variable
        to not Depends on type-handling.
    - debian/control:
      + Keep meta-packages for xbase-clients, xutils.
      + Change the Maintainer-field.
      + Add replaces for xinit since we now ship Xsession from x11-common.
        Ditto for xrgb as we ship rgb.txt in x11-common.
      + xserver-xorg: Add dependancy "OR xserver-xorg-video" because
        the restricted drivers provide that.
    - debian/local/Xsession:
      + If ~/.xsession-errors is bigger than 0.5MiB, truncate it to the last
        0.5MiB to avoid having it grow indefinitively. (This does not happen
        with gdm anyway since gdm cleans the file on login). (LP #60448)
    - debian/local/dexconf:
      + Uncoditionally re-enable ZAxisMapping in dexconf. (LP: #31827)
      + Add InputDevice entries for wacom.
      + Add extra bits for ps3fb xorg.conf.
      + Read xserver-xorg/config/device/extra_options key, parse it
        (first token is option name, rest of the line after first space
        is value), and add it as Option lines to the device section.
        (LP: #90109)
      + Add special case for i810 with 3M TouchScreen monitors to set a
        resolution of 800x600 and avoid probing since it will fail miserably
        in xserver-xorg.postinst. Also make sure to write Option "DisplayInfo"
        "False" in Device Section in dexconf if the above combination is
        matched otherwise the card will display extra unrequired info each
        time X attempts a startup. (touches also xserver-xorg.postinst.in)
      + Due to a very annoying DRI/DRM bug, make sure to use OldDmaInit
        when writing down the Device section for mga driver. This will make
        DRI working at least for AGP cards. PCI didn't work before and it will
        keep not working since the option does explicitly disable DRI for PCI.
        (LP: #27442)
      + Enable elographics driver when matching known machines.
      + Disable composite when using the fglrx driver. It does not support
        composition, and enabling it by default (as recently done in
        xorg-server) breaks DRI for fglrx. (LP: #90688)
    - debian/scripts/vars.i386:
      + Add xserver-xorg-input-elographics to XSERVER_XORG_INPUT_DEPENDS.
    - debian/xserver-xorg.postinst.in:
      + Add lt to list of non-Latin keymaps (LP: #38931).
      + Make sure to ask video driver on sparc even if autodetected. Some
        cards still require weird overrides (ati -> fbdev) that are not
        100% known in all combinations.
      + Skip video card autodetection if xforcevesa is set
        (LP #27020, #59618).
      + Detect keyboard layout configuration using /etc/default/console-setup
        if available.
      + Clean up duplicate keymaps in xserver-xorg.config.in and make sure
        they're all neatly alphabetised.
      + Map cf console keymap to ca(fr).
      + Map croat console keymap to hr. (LP: #43598)
      + Set default keyboard variant for French to oss (LP: #89835).
      + Map...