Patch #1048820 from Stefan Wehr: add insert-mode editing to Textbox.
Fix an off-by-one error I noticed.
diff --git a/Misc/ACKS b/Misc/ACKS
index 5c87ed1..36b7d44 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -696,6 +696,7 @@
 Aaron Watters
 Henrik Weber
 Corran Webster
+Stefan Wehr
 Zack Weinberg
 Edward Welbourne
 Cliff Wells