An issue raised by DRM people with the new drm core is how to stop users
shotting themselves in the foot when upgrading drm modules from CVS and
mixing up cores and drivers...
This patch (against DRM CVS) proposes a simple internal version that gets
passed from the module to the core, when built in-kernel, it gets set to
default DRM_INTERNAL_VERSION_KERNEL, when built in DRM CVS or snapshot, it
gets DRM_INTERNAL_VERSION_EXTERNAL, a core built in one will refuse to
load a module build in the other..
This is quite a simple solution that should stop the most obvious issue,
it doesn't stop people updating CVS drivers on top of themselves but my
view is anyone doing this is either following our scripts or knows what
they are doing...