lif: rename internal types

This is a followup to https://go-review.googlesource.com/30576.

Change-Id: I48bc5f1781275d2cef963876745fa59ac08b5eb5
Reviewed-on: https://go-review.googlesource.com/43070
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
3 files changed