Avoid GLib deprecation warnings when building gob.

Avoid GLib deprecation warnings when building gob.

The g_strdown functions are deprecated in GLib, we already have a
gob_strdown function which does the same thing with g_ascii_tolower,
but it seems a couple spots were missed.

There is also a call to g_strcasecmp which can be replaced by
g_ascii_strcasecmp.