testing: test.memprofilerate documentation is not accurate

[bradfitz]

The docs for the -test.memprofilerate flag say "if >= 0", but the code is simply greater, not greater than or equal:

~/go/src/testing$ git grep memProfileRate
testing.go:     memProfileRate   = flag.Int("test.memprofilerate", 0, "if >=0, sets runtime.MemProfileRate")
testing.go:     if *memProfileRate > 0 {
testing.go:             runtime.MemProfileRate = *memProfileRate

And the default is 512KB, not 0: https://golang.org/pkg/runtime/#pkg-variables

[gopherbot]

CL https://golang.org/cl/31332 mentions this issue.