ruby-postgres doesn't build with postgres 8.1

[Pat Maddox]

I've got postgresql-client-8.1.0 installed, and I'd like to install
the ruby-postgres bindings.  It seems to require
postgresql-client-7.4.9, and that conflicts with 8.1.0 so it won't
install.  This should compile against 8.1.0.

Thanks,
Pat