New debug scheme with explicit debug channels declaration.

diff --git a/windows/scroll.c b/windows/scroll.c
index 97523b0..2418384 100644
--- a/windows/scroll.c
+++ b/windows/scroll.c
@@ -19,6 +19,8 @@
 #include "sysmetrics.h"
 #include "debug.h"
 
+DEFAULT_DEBUG_CHANNEL(scroll)
+
 /*************************************************************************
  *             ScrollWindow16   (USER.61)
  */