runtime: Fix MStats struct to match Go MemStats struct.
runtime: Fix MStats struct to match Go MemStats struct.

Change-Id: Id371aa7ff3d5f290a47391eee360f1ddc830fefa
Reviewed-on: https://go-review.googlesource.com/16524
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

golang/gofrontend,golang/gofrontend,golang/gofrontend,golang/gofrontend