Remove directories of baseline images that we don't maintain

Remove directories of baseline images that we don't maintain

Also renaming "base" as "base-macpro" to be more descriptive.
I will add a base-macpro/README file in a subsequent CL (I fear what might
happen if I try to do that in the same CL as the directory rename).
Committed: http://code.google.com/p/skia/source/detail?r=2796