cmd/internal/gc, cmd/[56789]g: rename stackcopy to blockcopy

To avoid confusion with the runtime concept of copying stack.

Change-Id: I33442377b71012c2482c2d0ddd561492c71e70d0
Reviewed-on: https://go-review.googlesource.com/8639
Reviewed-by: Dave Cheney <dave@cheney.net>
Reviewed-by: Russ Cox <rsc@golang.org>
diff --git a/src/cmd/internal/gc/go.go b/src/cmd/internal/gc/go.go
index d399ebb..2d85f585 100644
--- a/src/cmd/internal/gc/go.go
+++ b/src/cmd/internal/gc/go.go
@@ -809,7 +809,7 @@
 	Sameaddr     func(*obj.Addr, *obj.Addr) bool
 	Smallindir   func(*obj.Addr, *obj.Addr) bool
 	Stackaddr    func(*obj.Addr) bool
-	Stackcopy    func(*Node, *Node, int64, int64, int64)
+	Blockcopy    func(*Node, *Node, int64, int64, int64)
 	Sudoaddable  func(int, *Node, *obj.Addr) bool
 	Sudoclean    func()
 	Excludedregs func() uint64