rubygems memory patch

This patch against RubyGems 1.1.1 improves memory usage by not keeping every unused gemspec permanently in memory. It should have low CPU impact as long as you do your gem requires up-front.

For MacPorts:

cd /opt/local/lib/ruby/site_ruby/1.8
curl \
  | sudo patch -p0

Incidentally, I used BleakHouse to track down which references were getting retained.