Update comments

mace/public/mace.h

@@ -19,6 +19,7 @@ namespace mace {
 const char *MaceVersion();
 
 enum DeviceType { CPU = 0, NEON = 1, OPENCL = 2, HEXAGON = 3 };
+
 enum MaceStatus { MACE_SUCCESS = 0, MACE_INVALID_ARGS = 1 };
 
 // MACE input/output tensor

mace/public/mace_types.h

@@ -3,7 +3,7 @@
 //
 
 // This file defines data types used by net creation and benchmark tools.
-// These APIs are not stable.
+// These APIs are not stable and should only be used by advanced users.
 
 #ifndef MACE_PUBLIC_MACE_TYPES_H_
 #define MACE_PUBLIC_MACE_TYPES_H_