time: clarify Equal docs

The docs used to imply that using == would compare Locations, but of
course it just compares Location pointers, which will have unpredictable
results depending on how the pointers are loaded.

Change-Id: I783c1309e476a9616a1c1c290eac713aba3b0b57
Reviewed-on: https://go-review.googlesource.com/32332Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/time/time.go

@@ -75,8 +75,7 @@ func (t Time) Before(u Time) bool {
 // Equal reports whether t and u represent the same time instant.
 // Two times can be equal even if they are in different locations.
 // For example, 6:00 +0200 CEST and 4:00 UTC are Equal.
-// This comparison is different from using t == u, which also compares
-// the locations.
+// Note that using == with Time values produces unpredictable results.
 func (t Time) Equal(u Time) bool {
 	return t.sec == u.sec && t.nsec == u.nsec
 }