testing: unordered examples are underdocumented

[ALTree]

Unordered examples (9323de3) are documented in go doc cmd/go:

If the last comment begins with "Unordered output:" then the output is compared to the comment, however the order of the lines is ignored

but not in go doc testing (which is the actual place where people will look for Examples documentation).

$ go doc testing | grep -c Unordered
0

and for the same reason there's nothing on https://golang.org/pkg/testing/#hdr-Examples.

[gopherbot]

CL https://golang.org/cl/37440 mentions this issue.