perf_counter tools: move helper library to util/*

Clean up the top level directory a bit by moving all the helper libraries
to util/*.[ch].

Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/Documentation/perf_counter/builtin.h b/Documentation/perf_counter/builtin.h
index 800f86c..d32318a 100644
--- a/Documentation/perf_counter/builtin.h
+++ b/Documentation/perf_counter/builtin.h
@@ -1,8 +1,8 @@
 #ifndef BUILTIN_H
 #define BUILTIN_H
 
-#include "util.h"
-#include "strbuf.h"
+#include "util/util.h"
+#include "util/strbuf.h"
 
 extern const char perf_version_string[];
 extern const char perf_usage_string[];