[gimp/f14] (3 commits) ...guard against crash due to quitting while DND is processed (#711952)

[Nils Philippsen]

Summary of changes:

  5b7e0b8... drop support for building with non-modular X (*)
  8daad80... ensure file-xpm plugin is built (#710207) (*)
  69b2723... guard against crash due to quitting while DND is processed  (*)

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