even if we don't have private members (yet). Also make class padding 8
pointers in all headers. This commit moves nothing to private, it just
makes all headers consistent and adjusts .c files accordigly.
This only helps to maintain proper includes in app/ and shouldn't
affect plug-ins at all, because these are supposed to only include the
main headers from libgimp/ since the beginning of time.
The gimpfootypes.h files do not have these guards, so we can continue
to maintain app/'s include policy that is very likely to error out if
wrong things are included.
Michael Natterer