Refine DebugHelper.h into Log.h.

This removes USE_FUNC_LOGGER from libbcc-config.mk.
diff --git a/lib/ExecutionEngine/ELFObjectLoaderImpl.cpp b/lib/ExecutionEngine/ELFObjectLoaderImpl.cpp
index 82eac5f..86e6efd 100644
--- a/lib/ExecutionEngine/ELFObjectLoaderImpl.cpp
+++ b/lib/ExecutionEngine/ELFObjectLoaderImpl.cpp
@@ -25,7 +25,7 @@
 #include "utils/serialize.h"
 
 #include "bcc/ExecutionEngine/SymbolResolverInterface.h"
-#include "bcc/Support/DebugHelper.h"
+#include "bcc/Support/Log.h"
 
 using namespace bcc;