Go 1.6 significantly improves pause times for large heaps, but it
improves them in many other situations as well, such as when goroutine
churn is high, allocation rate is high, or when there are many
finalizers. Hence, make the statement about pause times a bit more
general.

Change-Id: Ic034b1c904c39dd1d966ee7fa96ca8bbb3614e53
Reviewed-on: https://go-review.googlesource.com/19504Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>