glib2: require Ruby 1.9.3 or later
gdk3: require Ruby 1.9.3 or later
gtk3: require Ruby 1.9.3 or later
gvlc: require Ruby 1.9.3 or later
vte3: require Ruby 1.9.3 or later
Merge pull request #171 from myokoym/require-ruby-1-9-3-or-later

Require Ruby 1.9.3 or later

Patch by Masafumi Yokoyama. Thanks!!!