Cleaning up requires in glib2.rb


Currently, glib2.rb requires pathname, English, and thread. Pathname
is only used sporadically and can easily be replaced by File methods.
English is used for $POSTMATCH. I don’t think this is worth including
English for. It wolud be better to not even use $POSTMATCH or $’, but
that’s another topic. I see no use of thread glib2.rb. Is it used in