cmd/compile: rewrite %1v and %2v formats to %S and %L (short and long)

- also consistently use %v instead of %s when we have a (gc) Formatter
- rewrite done automatically using Formats test in -u (update) mode
- manual update of format strings that were not single string constants
- updated fmt.go, fmt_test.go accordingly
- fmt_test: permit "%T" always

Change-Id: I8f0704286aba5704600ad0c4a4484005b79b905d
Reviewed-on: https://go-review.googlesource.com/28954
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/compile/internal/gc/range.go

@@ -48,7 +48,7 @@ func typecheckrange(n *Node) {
 	toomany = 0
 	switch t.Etype {
 	default:
-		Yyerror("cannot range over %2v", n.Right)
+		Yyerror("cannot range over %L", n.Right)
 		goto out
 
 	case TARRAY, TSLICE:
@@ -104,7 +104,7 @@ func typecheckrange(n *Node) {
 		if v1.Name != nil && v1.Name.Defn == n {
 			v1.Type = t1
 		} else if v1.Type != nil && assignop(t1, v1.Type, &why) == 0 {
-			Yyerror("cannot assign type %v to %2v in range%s", t1, v1, why)
+			Yyerror("cannot assign type %v to %L in range%s", t1, v1, why)
 		}
 		checkassign(n, v1)
 	}
@@ -113,7 +113,7 @@ func typecheckrange(n *Node) {
 		if v2.Name != nil && v2.Name.Defn == n {
 			v2.Type = t2
 		} else if v2.Type != nil && assignop(t2, v2.Type, &why) == 0 {
-			Yyerror("cannot assign type %v to %2v in range%s", t2, v2, why)
+			Yyerror("cannot assign type %v to %L in range%s", t2, v2, why)
 		}
 		checkassign(n, v2)
 	}