* gegl/property-types/gegl-path.c: (subpath_changed),
(gegl_path_add_parameter_path), Make changes to subpaths cause a full
invalidation of the parent path object.
(gegl_path_stamp), (gegl_path_stroke): take parameter scaling factors
from "linewidth" and "opacity" path parameters if they are available.
* gegl/property-types/gegl-path.h:
* operations/external/stroke.c: (get_bounding_box), (process),
(gegl_chant_class_init): pass in extra information that might be
useful to limit un-needed composites of stamps outside the roi.

svn path=/trunk/; revision=2685