Fix the cmp implementation for variant values
Fix the cmp implementation for variant values

This was causing g_param_value_defaults to return 1
for GVariant values even when the value is clearly
different from the default.

This was showing up as gtk-builder-tool stripping
non-default values for GtkActionable::action-target
from ui files.

endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib