Add logging framework.

DEBUG messages are completely optimized out if NDEBUG is defined.

src/Storage.cpp

@@ -12,11 +12,10 @@
 
 #include "llvm/StringExtras.h"
 #include "Base64.h"
+#include "Log.h"
 
 using namespace nt;
 
-#define DEBUG(str) puts(str)
-
 ATOMIC_STATIC_INIT(Storage)
 
 Storage::Storage() {}