[gimp] (12 commits) ...plug-ins: in metadata editor and viewer only convert values to UTF-8 if they are not.

[Jehan <jehanp src gnome org>]

Summary of changes:

  d0f67fa... libgimpbase: fix incorrect reading of iptc tags that appear (*)
  599d91d... plug-ins: Refactor certain string handling into separate fu (*)
  26db975... plug-ins: fix incorrect reading of iptc tags that appear mo (*)
  786aaec... plug-ins: fix incorrect single/multi(ple) values for certai (*)
  c855590... plug-ins: fix incorrect struct used for comparison in metad (*)
  bd2f43b... plug-ins: Refactor cleaning xmp values into a separate func (*)
  879b374... plug-ins: fix not showing all values of iptc tags that appe (*)
  7cce45b... plug-ins: In metadata-editor always read iptc equivalent va (*)
  96c5d1c... plug-ins: add missing Iptc equivalents of Xmp tags in metad (*)
  47065df... plug-ins: let metadata-editor also save Iptc tags. (*)
  d004305... plug-ins: fix metadata-editor not saving Xmp.photoshop.Urge (*)
  3128047... plug-ins: in metadata editor and viewer only convert values (*)

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