The name-based heuristics fail too often to be on during "go test",
but we really want the printf vet check in "go test", so change to
a list of exactly which standard library functions are print-like.

For a later release we'd like to bring back checking for user-defined
wrappers, but in a completely precise way. Not for Go 1.10, though.

The new, more precise list includes t.Skipf, which caught some
mistakes in standard library tests.

Fixes #22936.

Change-Id: I110448e3f6b75afd4327cf87b6abb4cc2021fd0d
Reviewed-on: https://go-review.googlesource.com/83838
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>