Brush Datablock:

- Added a new Brush datablock, only used by image paint, but intended
  to be used in texture paint, vertex paint, weight paint and sculpt
  mode also.
- Being a datablock, these brushes can be saved, appended and linked.
  They have a fake user by default, to make sure they are saved even if
  not selected.

Image Painting:

- Replaced the img module with C code in imagepaint.c
- Airbrush is no longer a separate tool, but rather an option that can
  be used for soften, smear and clone also.
- Blend modes mix, add, subtract, multiply, darken and lighten have been
  added, code taken directly from vertex paint.

Note to project files maintainers:

- The img module was removed from SCons and Makefiles, and this should
  be done in other build systems also. I'll wait to remove the module
  from cvs, to not break compilation.

source/blender/include/blendef.h

@@ -317,6 +317,9 @@
 #define B_SIMA_USE_ALPHA	371
 #define B_SIMA_SHOW_ALPHA	372
 #define B_SIMA_SHOW_ZBUF	373
+#define B_BRUSHBROWSE		374
+#define B_BRUSHDELETE		375
+#define B_BRUSHLOCAL		376
 
 /* BUTS: 400 */
 #define B_BUTSHOME		401