Comment 12 for bug 42553

The xorg.conf script is done by a shell script: /usr/bin/dexconf
in the source: ~/xorg-7.2/debian/x11-common/usr/bin/dexconf

In it, it seems that all card are created with that ServerLayout section:
### SERVERLAYOUT

exec 4>"$DEXCONFTMPDIR/ServerLayout"
cat >&4 <<SECTION
Section "ServerLayout"
        Identifier "Default Layout"
        Screen "Default Screen"
        InputDevice "Generic Keyboard"
        InputDevice "Configured Mouse"
        InputDevice "stylus" "SendCoreEvents"
        InputDevice "cursor" "SendCoreEvents"
        InputDevice "eraser" "SendCoreEvents"
SECTION

Maybe the 3 lines should be commented out there, unless more cards need it then that don't need it, which I seriously doubt.