Merge branch 'upstream-jsoncpp' into update-jsoncpp

* upstream-jsoncpp:
  jsoncpp 2020-09-25 (9059f5ca)

Utilities/cmjsoncpp/include/json/forwards.h

@@ -13,17 +13,23 @@
 namespace Json {
 
 // writer.h
+class StreamWriter;
+class StreamWriterBuilder;
+class Writer;
 class FastWriter;
 class StyledWriter;
+class StyledStreamWriter;
 
 // reader.h
 class Reader;
+class CharReader;
+class CharReaderBuilder;
 
-// features.h
+// json_features.h
 class Features;
 
 // value.h
-typedef unsigned int ArrayIndex;
+using ArrayIndex = unsigned int;
 class StaticString;
 class Path;
 class PathArgument;