newUserFromSid() is extended so that the retriaval of the user home
path based on a user SID becomes possible.

(1) The primary method it uses is to lookup the Windows registry for
the following key:
  HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList\[SID]

If the key does not exist the user might not have logged in yet.
If (1) fails it falls back to (2)

(2) The second method the function uses is to look at the default home
path for users (e.g. WINAPI's GetProfilesDirectory()) and append
the username to that. The procedure is in the lines of:
  c:\Users + \ + <username>

The function newUser() now requires the following arguments:
  uid, gid, dir, username, domain
This is done to avoid multiple calls to usid.String() and
usid.LookupAccount("") in the case of a newUserFromSid()
call stack.

The functions current() and newUserFromSid() both call newUser()
supplying the arguments in question. The helpers
lookupUsernameAndDomain() and findHomeDirInRegistry() are
added.

This commit also updates:
- go/build/deps_test.go, so that the test now includes the
"internal/syscall/windows/registry" import.
- os/user/user_test.go, so that User.HomeDir is tested on Windows.

GitHub-Last-Rev: 25423e2a3820121f4c42321e7a77a3977f409724
GitHub-Pull-Request: golang/go#23822
Change-Id: I6c3ad1c4ce3e7bc0d1add024951711f615b84ee5
Reviewed-on: https://go-review.googlesource.com/93935Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>