Delete JSONCPP_DEPRECATED, use [[deprecated]] instead. (#978)

* delete JSONCPP_DEPRECATED, use [[deprecated]]

* add pragma warning(disable:4996)

* add error C2416

* update

* update

* update
diff --git a/include/json/writer.h b/include/json/writer.h
index 12fd36a..3280141 100644
--- a/include/json/writer.h
+++ b/include/json/writer.h
@@ -145,7 +145,7 @@
 /** \brief Abstract class for writers.
  * \deprecated Use StreamWriter. (And really, this is an implementation detail.)
  */
-class JSONCPP_DEPRECATED("Use StreamWriter instead") JSON_API Writer {
+class [[deprecated("Use StreamWriter instead")]] JSON_API Writer {
 public:
   virtual ~Writer();
 
@@ -165,7 +165,7 @@
 #pragma warning(push)
 #pragma warning(disable : 4996) // Deriving from deprecated class
 #endif
-class JSONCPP_DEPRECATED("Use StreamWriterBuilder instead") JSON_API FastWriter
+class [[deprecated("Use StreamWriterBuilder instead")]] JSON_API FastWriter
     : public Writer {
 public:
   FastWriter();
@@ -225,7 +225,7 @@
 #pragma warning(push)
 #pragma warning(disable : 4996) // Deriving from deprecated class
 #endif
-class JSONCPP_DEPRECATED("Use StreamWriterBuilder instead") JSON_API
+class [[deprecated("Use StreamWriterBuilder instead")]] JSON_API
     StyledWriter : public Writer {
 public:
   StyledWriter();
@@ -294,7 +294,7 @@
 #pragma warning(push)
 #pragma warning(disable : 4996) // Deriving from deprecated class
 #endif
-class JSONCPP_DEPRECATED("Use StreamWriterBuilder instead") JSON_API
+class [[deprecated("Use StreamWriterBuilder instead")]] JSON_API
     StyledStreamWriter {
 public:
   /**