[ruby-core:26212] Config.datadir in 1.9.1

In 1.8.6., Config.datadir('package') would give you the gem-relative
data directory for a gem.  In 1.9.1, Config doesn’t seem to even be
loaded at startup.  What happened?  What am I supposed to use instead?
 Even if you get Config loaded it still won’t work, as the gem’s paths
are already added to $LOAD_PATH, so Rubygems won’t load the
specification and thus Gem.datadir('package') will give a nil result.

Is this a bug or am I doing something wrong?