gapplication: Properly free the option_strings
gapplication: Properly free the option_strings

option_strings gets set in g_application_add_main_option, so it can
contain elements independent from packed_options.

https://bugzilla.gnome.org/show_bug.cgi?id=773303

johne53/MB3Glib,johne53/MB3Glib,johne53/MB3Glib,johne53/MB3Glib,endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib,johne53/MB3Glib,johne53/MB3Glib