Remove the G_GNUC_STRFTIME format check
Remove the G_GNUC_STRFTIME format check

This does not work, since g_date_time_format() supports
non-standard extensions such as %:::z, and this has
broken several consumers which use format errors, such
as ostree.

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