glib-demo: Remove use of deprecated gtk_dialog_get_action_area()

https://bugs.freedesktop.org/show_bug.cgi?id=82385
glib-demo: Replace use of deprecated gtk stock items

https://bugs.freedesktop.org/show_bug.cgi?id=82384
Makefile.am cleanups

Bug #79411
poppler: use poppler-data pkg-config for both cmake and autotools builds
Make sure e is always initialized
Update (C) years
0.26.4
Merge remote-tracking branch 'origin/poppler-0.26'