cmd/compile: rename T_old_DARRAY and update comments

Change-Id: Ifa3b1b1e5458e4f109828a476d37f1caf96fe14b
Reviewed-on: https://go-review.googlesource.com/21211
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/cmd/compile/internal/gc/bexport.go b/src/cmd/compile/internal/gc/bexport.go
index 4457ff3..03f2cf4 100644
--- a/src/cmd/compile/internal/gc/bexport.go
+++ b/src/cmd/compile/internal/gc/bexport.go
@@ -512,8 +512,8 @@
 		}
 		p.typ(t.Type)
 
-	case T_old_DARRAY:
-		// see p.param use of T_old_DARRAY
+	case TDDDFIELD:
+		// see p.param use of TDDDFIELD
 		p.tag(dddTag)
 		p.typ(t.Type)
 
@@ -664,9 +664,7 @@
 	t := q.Type
 	if q.Isddd {
 		// create a fake type to encode ... just for the p.typ call
-		// (T_old_DARRAY is not used anywhere else in the compiler,
-		// we use it here to communicate between p.param and p.typ.)
-		t = &Type{Etype: T_old_DARRAY, Type: t.Type}
+		t = &Type{Etype: TDDDFIELD, Type: t.Type}
 	}
 	p.typ(t)
 	if n > 0 {