* app/core/gimpimage.[ch]: make the parent parameter public in
add_layer(), add_layers(), add_channel() and add_vectors().

* app/vectors/gimpvectors-import.[ch]: add parent parameters to
  the vectors import functions.

* app/core/gimpchannelundo.[ch]
* app/core/gimplayerundo.[ch]
* app/vectors/gimpvectorsundo.[ch]
* app/core/gimpimage-undo-push.[ch]: remember the parent item when
  removing layers, channels and vectors.

* app/actions/channels-commands.c
* app/actions/debug-commands.c
* app/actions/edit-commands.c
* app/actions/layers-commands.c
* app/actions/vectors-commands.c
* app/core/gimp-edit.c
* app/core/gimpimage-duplicate.c
* app/core/gimpimage-merge.c
* app/core/gimpimage-quick-mask.c
* app/core/gimplayer-floating-sel.c
* app/core/gimpselection.c
* app/core/gimptemplate.c
* app/dialogs/file-open-dialog.c
* app/display/gimpdisplayshell-dnd.c
* app/text/gimptext-compat.c
* app/tools/gimptexttool.c
* app/tools/gimpvectortool.c
* app/widgets/gimptoo...