New debug scheme with explicit debug channels declaration.

diff --git a/files/drive.c b/files/drive.c
index 78806f4..93c2c1d 100644
--- a/files/drive.c
+++ b/files/drive.c
@@ -44,6 +44,9 @@
 #include "task.h"
 #include "debug.h"
 
+DECLARE_DEBUG_CHANNEL(dosfs)
+DECLARE_DEBUG_CHANNEL(file)
+
 typedef struct
 {
     char     *root;      /* root dir in Unix format without trailing / */