Running -copylocks over a large corpus generates 1507 warnings.
Of those, only 3 are from the new anonymous function check,
but they are all bugs.

Fixes #10927.

Change-Id: I2672f6871036bed711beec5f88bc39aa8b3b6a94
Reviewed-on: https://go-review.googlesource.com/11051Reviewed-by: Rob Pike <r@golang.org>