mate-dictionary: implicit declaration of g_mkdir
Remove deprecated g_thread_init
Fix deprecated functions

Remove, now unneeded, gdkkeysyms-compat.h include
Always use gtk_combo_box_text_new (since Gtk+ 2.24)
Gtk3: do not use gdk_cursor_unref
Gtk3: replace gtk_hpaned_new
Gtk3: replace gtk_widget_modify_font