Movies support for Cycles

This adds support of movie textures for Cycles rendering.

Uses the same builtin images routines as packed/generated images,
but with some extra non-rna hookups from blender_session side.

Basically, it's not so clear how to give access to video frames
via C++ RNA -- it'll require exposing ImBuf to API, doing some
threading locks and so. Ended up adding two more functions which
are actually bad level call, but don't consider it's so much bad
-- we have few bad calls already, which are actually related.

Changed a bit how builtin images names are passing to image
manager. Now it's not just an ID datablock name, but also a frame
number concatenated via '@' character, which makes itpossible to
easily know frame number to be used for movie images, without
adding extra descriptors to image manager.

Decoding of builtin name is a bit slower now, but it should be
still nothing in comparison with rendering complexity.

Also exposed image user's frame_current to python API, which
is needed to get absolute frame number of movie from node's
image user.

P.S. Generated/packed images are also using bad level call but
only does it to make things more clear here.  Either all images
are using C++ RNA here or no images does. That's the most clear
for now.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@53848 954f8c5b-7b00-dc11-b283-0030488c597c
Style cleanup: spaces at the end of lines

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@53849 954f8c5b-7b00-dc11-b283-0030488c597c