Print out the escaped Value in PrtMap (#553)

Currently, the escaped Key value for each entry in the map is printed
instead of the escaled Value; change it to print the Value as expected.

Src/PRuntimes/PCSharpRuntime/Values/PrtMap.cs

@@ -202,7 +202,7 @@ public string ToEscapedString()
             foreach (KeyValuePair<IPrtValue, IPrtValue> value in map)
             {
                 string k = value.Key == null ? "null" : value.Key.ToEscapedString();
-                string v = value.Value == null ? "null" : value.Key.ToEscapedString();
+                string v = value.Value == null ? "null" : value.Value.ToEscapedString();
                 sb.Append(sep);
                 sb.Append("<");
                 sb.Append(k);