Use std::unique_ptr instead of std::scoped_ptr

scoped_ptr has never been a part of the C++ standard - perhaps it's been
confused with boost::scoped_ptr. Anyhow, std::unique_ptr is the
replacement for the now-deprecated std::auto_ptr.

Author: AbigailBuccaneer

src/lib_json/json_reader.cpp

@@ -44,7 +44,7 @@ static int       stackDepth_g = 0;  // see readValue()
 namespace Json {
 
 #if __GNUC__ >= 6
-typedef std::scoped_ptr<CharReader> const  CharReaderPtr;
+typedef std::unique_ptr<CharReader> const  CharReaderPtr;
 #else
 typedef std::auto_ptr<CharReader>          CharReaderPtr;
 #endif

src/lib_json/json_writer.cpp

@@ -55,7 +55,7 @@
 namespace Json {
 
 #if __GNUC__ >= 6
-typedef std::scoped_ptr<StreamWriter> const  StreamWriterPtr;
+typedef std::unique_ptr<StreamWriter> const  StreamWriterPtr;
 #else
 typedef std::auto_ptr<StreamWriter>          StreamWriterPtr;
 #endif