gtestutils: add "options" to g_test_init(), make option-argv0 use gtester

gtestutils: add "options" to g_test_init(), make option-argv0 use gtester

Declare that the previously-unused "..." argument to g_test_init() is
actually a NULL-terminated list of strings indicating testing options,
and add an option "no_g_set_prgname", which keeps g_test_init() from
calling g_set_prgname(). Then we can port glib/tests/option-argv0 to
use gtester, by passing that option.

https://bugzilla.gnome.org/show_bug.cgi?id=711796