time: parse WITA timezone correctly

WITA stands for Asia/Makassar IANA timezone
https://en.wikipedia.org/wiki/Asia/Makassar

Fixes #18251

Change-Id: I5896efb8052593afb4e51ae4a34b574a8206d4dc
Reviewed-on: https://go-review.googlesource.com/34253Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/time/format.go

@@ -1101,8 +1101,9 @@ func parseTimeZone(value string) (length int, ok bool) {
 		if value[4] == 'T' {
 			return 5, true
 		}
-	case 4: // Must end in T to match.
-		if value[3] == 'T' {
+	case 4:
+		// Must end in T, except one special case.
+		if value[3] == 'T' || value[:4] == "WITA" {
 			return 4, true
 		}
 	case 3:

src/time/format_test.go

@@ -405,6 +405,7 @@ var parseTimeZoneTests = []ParseTimeZoneTest{
 	{"ESAST hi", 5, true},
 	{"ESASTT hi", 0, false}, // run of upper-case letters too long.
 	{"ESATY hi", 0, false},  // five letters must end in T.
+	{"WITA hi", 4, true},    // Issue #18251
 }
 
 func TestParseTimeZone(t *testing.T) {