Move hot utf routines into -inl.h.

Change-Id: I7050d8282a7e5870b2bf671d6867c57625e00ccc
diff --git a/runtime/utils.cc b/runtime/utils.cc
index dcfe8a7..28ee58c 100644
--- a/runtime/utils.cc
+++ b/runtime/utils.cc
@@ -34,7 +34,7 @@
 #include "mirror/string.h"
 #include "object_utils.h"
 #include "os.h"
-#include "utf.h"
+#include "utf-inl.h"
 
 #if !defined(HAVE_POSIX_CLOCKS)
 #include <sys/time.h>