gobject-2.0: Add some missing symbols
gobject-2.0: Add some missing symbols

G_SIGNAL_FLAGS_MASK, G_SIGNAL_MATCH_MASK, g_source_set_closure,
g_source_set_dummy_callback

GNOME/vala,GNOME/vala,frida/vala,GNOME/vala,frida/vala,GNOME/vala,frida/vala,frida/vala,frida/vala