[Bf-codereview] New dilation code for bake filtering (issue4822045)

[g.ulairi at gmail.com]

Reviewers: bf-codereview_blender.org,

Description:
Hello everyone,

Morten Mikkelsen (in fact, not only him) noticed really bad things with
Blender's bake filtering (this was discussed in our mailing list).

Morten provided new code which is supposed to replace our filtering.
I've tried to blender-ize it so it should fit our code conventions.

Also this patch increases maximal margin from 32 to 64. It's needed
because baker is now used for really large images.

Please review this at http://codereview.appspot.com/4822045/

Affected files:
   source/blender/imbuf/IMB_imbuf.h
   source/blender/imbuf/intern/filter.c
   source/blender/makesrna/intern/rna_scene.c
   source/blender/render/intern/source/rendercore.c