kernel: Bump to 3.12.23

effects: Initial code for 3d sbs to anaglyph

video_decode: Fix nBufferSize setting getting lost
See: https://github.com/raspberrypi/firmware/issues/240#issuecomment-46690373

video_render: Add command for querying render statistics
See: https://github.com/raspberrypi/firmware/issues/287#issuecomment-46776904

hvs: Add gencmd to configure only updating display list on odd/even field
See: https://github.com/raspberrypi/firmware/issues/292