Fix T37572: text editor scrolling not working well with Mac trackpad panning.

The trackpad would give isolated mouse pan events with a distance smaller than
one line or character. For other 2D views this is all accumulated in floats,
but in the text editor it only keeps track of integers, and the small mouse pan
events got lost due to rounding.

Now it keeps track of sub-line or sub-character scroll offsets to avoid this.
Hide the 3D cursor in a few cases where it is unneeded (active object is
in sculpt mode or image paint mode and no clone tool is active)
minor style and comment fix.
Implement GPU-side dither

Summary:
Uses some magic pseudo-random which is actually a
texture coordinate hashing function.

TODOs:
- Dither noise is the same for all the frames.
- It's different from Floyd's dither we've been
  using before.
- Currently CPU and GPU dithering used different
  implementation. Ideally we need to use the same
  dither in CPU.

Reviewers: brecht

Reviewed By: brecht

Differential Revision: http://developer.blender.org/D58
Interface / PointCache: Remove name fields here as well, not needed anymore due to direct rename in uiList.
Interface / Particles: Fix bad alignment in Rotation panel, sub layout missed the flag.
Image cache rewrite to using generic movie cache

Summary:
Behaves very much the same as cache for Movie Clip datablock:

- Image now have `MovieCache *cache` field which replaced
  legacy `ListBase ibufs`.

  This allows image datablock to easily keep of image
  buffers which are owned by itself. This field isn't
  saved to the file and getting restored on undo steps.

  However, cache limit is global for movies, sequences
  and image datablocks now. So overall cached image buffers
  size will not go above cache limit size in user
  preferences.

- Image buffers which are marked as BITMAPDIRTY will never
  be freed from the cache.

- Added utility function to iterate over image buffers
  saved in movie cache.

- Movie cache cleanup check callback now have ImBuf argument
  which can be used in a condition of cleanup.

- Added some utility functions which replaces legacy ibufs
  iterations with image cache iteration which happens from
  inside a lock.

- Fixed `image_mem_size()` which was only counting one of
  the buffers if both float and byte buffer present.

Additional notes:

- `BKE_image_get_first_ibuf()` is rather stupid, but direct
  access to ibufs->first was also the same stupid idea.

  Would consider avoid this function is another project.

- There are some places which doesn't look threadsafe, but
  they already were not so much threadsafe anyway before.

  So think not a big deal with solving this later.

Finally solves infinite memory usage by image sequences! :)

Reviewers: brecht, campbellbarton

Reviewed By: brecht

CC: sebastian_k

Differential Revision: http://developer.blender.org/D95
Merge branch 'master' of http://git.blender.org/blender