MSVC warning fixes in tests

- only use "#pragma GCC" on GCC-compatible compilers
- suppress deprecation warnings also on MSVC

src/test_lib_json/main.cpp

@@ -3,8 +3,12 @@
 // recognized in your jurisdiction.
 // See file LICENSE for detail or copy at http://jsoncpp.sourceforge.net/LICENSE
 
+#if defined(__GNUC__)
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+#elif defined(_MSC_VER)
+#pragma warning(disable : 4996)
+#endif
 
 #include "jsontest.h"
 #include <json/config.h>
@@ -2591,4 +2595,6 @@ int main(int argc, const char* argv[]) {
   return runner.runCommandLine(argc, argv);
 }
 
+#if defined(__GNUC__)
 #pragma GCC diagnostic pop
+#endif