Drop Gck list API
gck provided some APIs that made working with lists of GObject
s
easier. GLib has for a long time added API that works well enough for
the same use case, like g_list_copy_deep()
, g_list_free_full()
and
more recently also g_clear_list()
, so use those instead.
This commit also bumps the required GLib version to a more modern 2.64
(which is needed for the g_clear_list()
API).