Implement bootvid driver for Xbox

Bootvid driver is used to display ReactOS boot animation, NT native console applications, kernel debugger in screen mode, and BSoD's.

Xbox have nVidia NV2A video chip that should be used to display bootvid graphics via framebuffer.

Support for it can be added depending on build target, so modifying bootvid CMakeLists like this should be appropriate:

 elseif(SARCH STREQUAL "xbox")

     list(APPEND SOURCE

         xbox/bootvid.c

         xbox/bootdata.c)

FreeLoader have fully-fledged Xbox video support, so you may refer to its source code: https://git.reactos.org/?p=reactos.git;a=blob;f=boot/freeldr/freeldr/arch/i386/xboxvideo.c;h=bcb70d0ce1083c2cda2d917b556e1d0ad43454ee;hb=HEAD