[glade] (7 commits) Non-fast-forward update to branch tintou/listbox-placeholder

[Alberto Fanjul <albfan src gnome org>]

The branch 'tintou/listbox-placeholder' 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:

  18dee8f... Allow to specify placeholder to GtkListBox
  ea45a0e... Remove added widgets if placeholder is disabled

Commits added to the branch:

  ff86575... Convert the README to markdown (*)
  4730383... Add new maintainer (*)
  216506a... Update mail lists (*)
  2d276ea... gladeui: fix several tiny memory leaks found with valgrind (*)
  903bab0... gladeui: Fix crash on drag-n-drop (*)
  5f79e8d... Allow to specify placeholder to GtkListBox
  dd74eaf... Remove added widgets if placeholder is disabled

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