They are not exported and not used in the compiler or standard library.

Change-Id: Ie1d210464f826742d282f12258ed1792cbd2d188
Reviewed-on: https://go-review.googlesource.com/43135
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>