[gimp] (9 commits) Non-fast-forward update to branch wip/nielsdg/gi-constants

[Jehan <jehanp src gnome org>]

The branch 'wip/nielsdg/gi-constants' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  c7b3f78... Make sure to use % for constants
  ba6301a... Use "Returns:" to annotate return values
  14562ef... Add (nullable) if applicable

Commits added to the branch:

  0787510... libgimp: add gimp_procedure_add_(argument|return_value)_fro (*)
  2c4a8c8... libgimp, app: allow usage of GParamSpecString procedure arg (*)
  04598b1... plug-ins: use new gimp_procedure_add_*_from_property() in P (*)
  6a1df5b... libgimpwidgets: fix a copy-paste bug in function docs. (*)
  58b3ca8... plug-ins: port python-console to new API. (*)
  b6e6f0b... libgimp: gimplegacy not introspected anymore. (*)
  746a72b... Make sure to use % for constants
  1dda601... Use "Returns:" to annotate return values
  5f92ced... Add (nullable) if applicable

(*) This commit already existed in another branch; no separate mail sent