* gegl/buffer/gegl-tile.h: removed flags from tile, as well as the
only user the for now deprecated quarter dirtying code. Not storing
per tile flags simplifies the tile storage backends, adding this back
can be considered with a working implementation.
* gegl/buffer/gegl-tile-source.h: 
* gegl/buffer/gegl-tile-backend-file.c:
* gegl/buffer/gegl-tile-backend-ram.c:
* gegl/buffer/gegl-tile-backend-tiledir.c:
* gegl/buffer/gegl-tile-handler-log.c:
* gegl/buffer/gegl-tile-handler-zoom.c:
* gegl/buffer/gegl-tile.c: refactored to use a much smaller recurse
function and removed defunct quarter dirtying code in favor of voiding
all smaller versions of a tile.

svn path=/trunk/; revision=2242