leveldb: A+C: ChaiShushan (individual CLA).

R=adg, alex.brainman, bradfitz
CC=golang-dev
https://codereview.appspot.com/36050044
leveldb-go: implement file lock on windows.

R=nigeltao, alex.brainman
CC=golang-dev
https://codereview.appspot.com/35380043

Committer: Nigel Tao <nigeltao@golang.org>