New debug scheme with explicit debug channels declaration.

diff --git a/graphics/mapping.c b/graphics/mapping.c
index ee9a090..15b6160 100644
--- a/graphics/mapping.c
+++ b/graphics/mapping.c
@@ -7,6 +7,8 @@
 #include "dc.h"
 #include "debug.h"
 
+DEFAULT_DEBUG_CHANNEL(gdi)
+
 
 /***********************************************************************
  *           MAPPING_FixIsotropic