time: set Local.name on windows

Local.String() returns "Local" on every OS, but windows.
Change windows code to do like others.

Updates #15568

Change-Id: I7a4d2713d940e2a01cff9d7f5cefc89def07546a
Reviewed-on: https://go-review.googlesource.com/23078Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/time/zoneinfo_test.go

@@ -61,3 +61,12 @@ func TestFirstZone(t *testing.T) {
 		}
 	}
 }
+
+func TestLocationNames(t *testing.T) {
+	if time.Local.String() != "Local" {
+		t.Errorf(`invalid Local location name: got %q want "Local"`, time.Local)
+	}
+	if time.UTC.String() != "UTC" {
+		t.Errorf(`invalid UTC location name: got %q want "UTC"`, time.UTC)
+	}
+}

src/time/zoneinfo_windows.go

@@ -140,6 +140,8 @@ func pseudoUnix(year int, d *syscall.Systemtime) int64 {
 func initLocalFromTZI(i *syscall.Timezoneinformation) {
 	l := &localLoc
 
+	l.name = "Local"
+
 	nzone := 1
 	if i.StandardDate.Month > 0 {
 		nzone++