Thanks to juston_li, there is a one-line fix to enable the latest NVIDIA drivers to compile with Kernel 3.18-rc1

See: https://devtalk.nvidia.com/default/topic/783364/linux/343-22-driver-incompatible-with-linux-3-18-/

The fix there is for Beta version 343.22, but I applied it to main version 340.46, as follows:

In NVIDIA-Linux-x86_64-340.46/kernel/nv-drm.c , at line 19, change

#if defined(NV_DRM_AVAILABLE)

#include <drm/drmP.h>

to

#if defined(NV_DRM_AVAILABLE)

#include <drm/drmP.h>
#include <drm/drm_gem.h>

Then re-compile..

Robert Gadsdon.  October 20, 2014.