cmd/compile: remove unused Type.Printed field

Change-Id: Iff2b1507dce08ef7c27085c8e0f45d0e3e88c476
Reviewed-on: https://go-review.googlesource.com/28152
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

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

@@ -153,7 +153,6 @@ type Type struct {
 	Etype      EType // kind of type
 	Noalg      bool  // suppress hash and eq algorithm generation
 	Trecur     uint8 // to detect loops
-	Printed    bool  // prevent duplicate export printing
 	Local      bool  // created in this file
 	Deferwidth bool
 	Broke      bool  // broken type definition.

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

@@ -3492,7 +3492,6 @@ func copytype(n *Node, t *Type) {
 	t.methods = Fields{}
 	t.allMethods = Fields{}
 	t.Nod = nil
-	t.Printed = false
 	t.Deferwidth = false
 
 	// Update nodes waiting on this type.