important issues:

* implement PF_IMAGE, PF_DRAWABLE etc... either in perl or make
  gimpui.h somehow available (hmm...)

not-so-important issues:

* tile & region functions -> make them piddles! (PDL)
* return values for run()
* unimplemented functions:
gimp_drawable_mask_bounds
gimp_drawable_offsets
*tile* functions
*rgn* functions
gimp_gradients_get_list
gimp_gradients_sample_uniform
gimp_gradients_sample_custom

* default function parameters (with hash %defaults?)
* gimp_text(text => "hallo", family => "engraver", size => 20);

