xf86-video-nestedv: driver to run Xorg on top of Xorg or something else

= Usage =

This is how I test it:
    X -config my.conf -noreset -retro :1
    (if your Xorg server is old you might need "-sharevts vt7", in case your
    bottom-layer X runs on vt7)

My xorg.conf:

-- begin xorg.conf --
Section "ServerFlags"
    Option "AutoEnableDevices" "false"
    Option "AutoAddDevices" "false"
EndSection

Section "Device"
    Identifier "device1"
    Driver "nestedv"
    Option "Display" ":0"     # you can omit this
EndSection

Section "Screen"
    Identifier "screen1"
    Device "device1"
    DefaultDepth 24
    Option "Origin" "100 100" # you can omit this
    SubSection "Display"
        Depth 24
        Modes "640x480"
    EndSubSection
EndSection

Section "ServerLayout"
    Identifier "layout1"
    Screen "screen1"
EndSection
-- end xorg.conf --

If you want to have an input device you need 3 things:
- add another input device to your machine
- configure your bottom-layer xorg.conf to _not_ use that device (you'll
  probably have to disable input hotplug and add InputDevice sections in
  xorg.conf)
- configure your top-layer xorg.conf to use that device
In the future I'll write xf86-input-nestedi so you'll be able to use it =)

You can also have more than one screen with this driver. Here's an example of a
xorg.conf with 2 screens and a mouse:

-- begin xorg.conf --
Section "ServerFlags"
    Option "AutoEnableDevices" "false"
    Option "AutoAddDevices" "false"
EndSection

Section "Device"
    Identifier "device1"
    Driver "nestedv"
EndSection
Section "Device"
    Identifier "device2"
    Driver "nestedv"
EndSection

Section "InputDevice"
    Identifier "mouse1"
    Driver "evdev"
    Option "device" "/dev/input/event7"
EndSection

Section "Screen"
    Identifier "screen1"
    Device "device1"
    DefaultDepth 24
    SubSection "Display"
        Depth 24
        Modes "640x480"
    EndSubSection
EndSection
Section "Screen"
    Identifier "screen2"
    Device "device1"
    DefaultDepth 24
    SubSection "Display"
        Depth 24
        Modes "640x480"
    EndSubSection
EndSection

Section "ServerLayout"
    Identifier "layout1"
    Screen "screen1"
    Screen "screen2" RightOf "screen1"
    InputDevice "mouse1"
EndSection
-- end xorg.conf --