[gentoo-user] System clean-up - removing unneeded packages *and* dependencies not used by other packages

[Tanstaafl]

Subject says it all...

I've had openldap installed on my system since forever but never used it
(always meant to, but honestly I really don't need it).

Now I'm wanting to uninstall unused stuff before switching gcc versions
and recompiling system and world.

Whats the best way to uninstall a package - in this case, openldap, but
really for any package - and get all of the dependencies it pulls in,
but only ones that are not required for other unrelated (to openldap)
packages?

Thanks...