runtime, cmd/link: minor cleanup

runtime, cmd/link: minor cleanup

Fix some comments.
Adjust capitalization for initialisms.
Use a println directly instead of emulating it.

Change-Id: I0d8fa0eb39547e2db8113fd0358136285b86f16a
Reviewed-on: https://go-review.googlesource.com/c/go/+/351462
Trust: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>