71db3dc120af os: make SameFile handle paths like c:a.txt properly
ff34a3e84dc0 net: fix CNAME resolving on Windows
LGTM=r
R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/130250043
Also zsyscall_windows_386.go and zsyscall_windows_amd64.go
have same contents, so merge them into single file.
LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/124430043