net: fix crashing Read/Write when passed empty slice on windows
net: fix crashing Read/Write when passed empty slice on windows

Fixes issue 921.

R=rsc
CC=golang-dev
http://codereview.appspot.com/1862043

Committer: Alex Brainman <54ba58c8441b5eff861de6b4e5ee46baf086b142@gmail.com>

tav/go,tav/go,tav/go,tav/go,tav/go,tav/go,tav/go