g_test_subprocess: record raw wait status and interpret it later
g_test_subprocess: record raw wait status and interpret it later

This avoids losing information that might be useful for later debugging.

(Modified by Philip Withnall to add comments to child_status and
test_trap_last_status.)

https://bugzilla.gnome.org/show_bug.cgi?id=748534

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