acme: implement Cmd-Shift-Z for Redo on Mac

Change-Id: Ie9332ed473609bd6ca156be0843dc5411cbf7b93
Reviewed-on: https://plan9port-review.googlesource.com/2941
Reviewed-by: Russ Cox <rsc@swtch.com>

src/cmd/acme/text.c

diff --git a/src/cmd/acme/text.c b/src/cmd/acme/text.c
index 7634d92..c53694c 100644
--- a/src/cmd/acme/text.c
+++ b/src/cmd/acme/text.c
@@ -757,6 +757,10 @@
 	 	typecommit(t);
 		undo(t, nil, nil, TRUE, 0, nil, 0);
 		return;
+	case Kcmd+'Z':	/* %-shift-Z: redo */
+	 	typecommit(t);
+		undo(t, nil, nil, FALSE, 0, nil, 0);
+		return;		
 
 	Tagdown:
 		/* expand tag to show all text */