it used to be a typedef to gpointer and actually was a cmsHPROFILE.
Change its API to be more "standard", remove the public close()
function. The object caches both the cmsHPROFILE and the data/length
ICC blob, so conversions between the two become obsolete (simply call
get_lcms_profile() or get_icc_profile()).
Adapt everything to the new API, but port it in a naive way for now,
the code doesn't take advantage of the new possibilities yet (like
refcounting).
Which will have proper API to deal with an image's color profile (no
parasites, no ICC blobs). So far contains gimp_image_get_color_profile()
and gimp_image_set_color_profile().