Update nanoCLR_DataType.cs (#10)

Author: josesimoes

source/MetadataProcessor.Core/Utility/nanoCLR_DataType.cs

@@ -1,4 +1,4 @@
-//
+//
 // Copyright (c) 2019 The nanoFramework project contributors
 // Original work from Oleg Rakhmatulin.
 // See LICENSE file in the project root for full license information.
@@ -31,6 +31,16 @@ internal enum nanoCLR_DataType : byte
         DATATYPE_TIMESPAN, // 8 bytes     // Shortcut for System.TimeSpan
         DATATYPE_STRING,
 
+        // This is the last type that doesn't need to be relocated
+        DATATYPE_LAST_NONPOINTER = DATATYPE_TIMESPAN,
+        // All the above types don't need fix-up on assignment
+        DATATYPE_LAST_PRIMITIVE_TO_PRESERVE = DATATYPE_R8,
+        // All the above types can be marshaled by assignment.
+        DATATYPE_LAST_PRIMITIVE_TO_MARSHAL = DATATYPE_TIMESPAN,
+
+        // All the above types don't need fix-up on assignment.
+        DATATYPE_LAST_PRIMITIVE = DATATYPE_STRING,
+
         DATATYPE_OBJECT, // Shortcut for System.Object
         DATATYPE_CLASS, // CLASS <class Token>
         DATATYPE_VALUETYPE, // VALUETYPE <class Token>